2010 RWISO Journal - Roth Williams International Society of ...

Contents 

Volume 2, No. 1, September 2010 

Letter from RWISO President, Samuel B. King, DDS, MS 

Letter from Editor-In-Chief, Thomas Chubb, DDS 

News from the Roth Williams Teaching Centers 

The Roth Williams Legacy Fund (RWLF) — Committee Report 

Ryan K. Tamburrino, DMD ■ Normand S. Boucher, DDS 

Robert L. Vanarsdall, DDS ■ Antonino G. Secchi, DMD, MS 

The Transverse Dimension: Diagnosis and Relevance to Functional 

Occlusion 

Byungtaek Choi, DDS, MS, PhD 

Hinge Axis: The Need for Accuracy in Precision Mounting: Part 2 

Michael J. Gunson, DDS, MD ■ G. William Arnett, DDS, FACD 

Condylar Resorption, Matrix Metalloproteinases, and Tetracyclines 

Dori Freeland, DDS, MS ■ Theodore Freeland, DDS, MS 

Richard Kulbersh, DMD, MS, PLC ■ Richard Kaczynski, BS, MS, PhD 

Comparison of Maxillary Cast Positions Mounted from a True Hinge 

Kinematic Face-Bow vs. an Arbitrary Face-Bow in Three Planes of Space 

Jina Lee Linton, DDS, MA, PhD, ABO ■ Woneuk Jung, DDS 

The Effect of Tooth Wear on Postorthodontic Pain Patients: Part 2 

Andrew Girardot, DDS, FACD 

Physiologic Treatment Goals in Orthodontics 

Wesley M. Chiang, DDS, MS ■ Theodore Freeland, DDS, MS 

Richard Kulbersh, DMD, MS, PLC ■ Richard Kaczynski, BS, MS, PhD 

Effect of Gnathologic Positioner Wear on Maximum Intercuspation 

CR Disharmony 

RWISO Journal | September 2010 

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RWISO JOURNAL 

SEPTEMBER 2010 VOL. 2, NO. 1 

EDITOR IN CHIEF 

Dr. Thomas K. Chubb 

EXECUTIVE DIRECTOR/ADVERTISING SALES 

Jeff Milde 

MANAGING EDITOR 

Anne Evers 

CREATIVE DIRECTORS 

Brad Reynolds (www.integralartandstudies.com) 

BOARD OF DIRECTORS 

President 

Dr. Sam King 

6460 Far Hills Avenue 

Centerville, OH 45459 USA 

937-433-9530 

samuel_king@hotmail.com 

President Elect 

Dr. Douglas Knight, DMD 

3210 Westport Green Place 

Louisville, KY 40241 USA 

502-327-6453 

knightortho@insightbb.com 

Vice President 

Dr. Renato Cocconi 

Via Traversante, San Leonardo 1 

43100 Parma, Italy 

+0521-273682 

orthosmile@studiococconi.it 

Secretary 

Dr. Eunah Choi 

Somang BD 2F, 907-1 

Bangbae 1 Dong 

Seocho Gu 

Seoul, 137-842 Korea 

+822-583-2275 

orthoi@hanmail.net 

Treasurer 

Dr. John F. Lawson, MS 

2460 Nwy 63 North 

Rochester, MN 55906 USA 

507-282-6447 

jlawdds@aol.com 

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Immediate Past President 

Dr. Darrell Havener 

1420 West Canal Court, 

Suite 200 

Littleton, CO 80120 USA 

303-791-2021 

dhavener@gmail.com 

Executive Director 

Jeff Milde 

1712 Devonshire Road 

Sacramento, CA 95864 USA 

916-270-2013 

j.milde@mra-sf.com 

COUNCIL MEMBERS 

Region I - Asia 

Dr. Satoshi Adachi 

#202, 5-11-8 Minoh 

Minoh, Osaka 562-0001 Japan 

+81-72-724-2866 

teeth@adachi-ortho.com 


Somang BD 2F, 907-1 

Bangbae 1 Dong 

Seocho Gu 

Seoul, 137-842 Korea 

+822-583-2275 

orthoi@hanmail.net 

RWISO Journal is published by the Roth Williams International Society 

of Orthodontists. 

Copyright © 2010 RWISO. All Rights Reserved. 

ISSN 2154-4395 (print) 

ISSN 2154-4409 (online) 

Reproduction whole or in part in any form or medium without express 

written permission of RWISO is prohibited. Information furnished in 

this journal is believed to be accurate and reliable; however, no responsibility 

is assumed for inaccuracies or for the information’s use. 

Postmaster: 

Send address changes to 

RWISO 


Sacramento, CA 95864 

RWISO Journal 

Roth Williams International Society of Orthodontists 


Sacramento, CA 95864 USA 

Phone: 916-270-2013 

Fax: 866-746-3815 

info@rwiso.org 

We welcome your responses to this publication. Please send comments, 

subscriptions, advertising and submission requests to: info@rwiso.org 

The Roth Williams International Society of Orthodontics is the embodiment 

of a philosophical and technological transformation: addition of 

physiologic to anatomics from a foundation of function and esthetics. 

Region II - Europe 

Dr. Claudia Aichinger 

Billrothstr. 58 

Vienna, A-1190 Austria 

+43-1-367-7222 

smile@draichinger.at 


Via Traversante, San Leonardo 1 

43100 Parma, Italy 

+0521-273682 

orthosmile@studiococconi.it 

Dr. Domingo Martin 

Plaza Bilbao 2-2A 

San Sebastian, 20005 Spain 

+34-943-427-814 

martingoenaga@arrakis.es 

Region III - USA, Canada 

Dr. Ramon Marti, MSC 

281 Oxford Street E. 

London, Ontario N6A 1V3 

Canada 

519-672-7740 

rmarti3@hotmail.com 

Region IV - South America 

Dra. Solange M. deFantini, MSD 

Al Janu 176 cj 42 

Sao Paulo, SP 01420-002 Brazil 

+55-11-3081-8440 

smfantin@usp.br 

Dra. Marisa Gianesella Bertolaccini 

Rua Tabapuã, 649 - Conj. 83 

Itaim Bibi, São Paulo, SP, 04533- 

012 Brazil 

+11- 505-25417 

mgianesella.odonto@gmail.com

Letter from the President 

Samuel B. King, DDS, MS 

RWISO President 

The world is changing rapidly. Technology is enabling us to do things never 

before possible. Orthodontics is changing too. New technologies, evolution 

of procedures, ease in obtaining information are just a few of the things that 

are advancing the orthodontic profession. The Roth Williams International 

Society of Orthodontists continues to evolve to provide the very best for our 

patients, but as we move forward with these new technologies, we are ever 

mindful of our treatment goals and the standards of our philosophy. 

The RWISO Journal embodies our commitment to remain true to our treatment 

goals and the standards of our philosophy. As orthodontic treatment 

changes, it is our duty to ensure, through evidence-based research, that new 

techniques and modalities achieve our goals and maintain our standards. Our 

Journal serves to educate our global organization about these advancements 

so that our members can confidently deliver the Roth Williams goals and 

standards to their patients. 

The Roth Williams International Society of Orthodontists is in the midst of 

an exciting time. Today we are able to treat our patients better than ever before 

with exciting new advancements in our profession. It is truly a great time 

to be part of the Roth Williams International Society of Orthodontists. 

Respectfully, 

Samuel B. King, DDS, MS 

RWISO President 


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Letter from the Editor 

Thomas Chubb, DDS 

Editor-In-Chief of RWISO Journal 

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Dr. Thomas Chubb | Letter from the Editor 

I would first like to thank all the authors in this year’s Journal for the amount of time 

and energy they devoted to giving us another first class issue. They are the lifeblood of 

the RWISO Journal. I know the authors would be interested in your feedback. Their 

e-mail addresses are listed on their articles, so please contact them with any comments 

you might have. I apologize to any author whose submission did not make it into this 

issue. We are already working on the next issue, which we hope will come out between 

now and the next meeting. 

I would like to thank Anne Evers, our managing editor, and Irene Elmer, our copy 

editor, for all their hard work and professionalism. Many of the authors have felt the 

sting of Irene’s sharp pen and the exacting revisions they both required. Their many 

hours of hard work were needed to bring this issue to fruition. I would also like to 

thank all our sponsors who contributed generously to help publish this issue and to 

Jeff Milde for all his logistical support. 

After reading the reports from the Roth Williams regional directors, I was struck by 

the level of involvement in education to which this group has devoted itself. Unfortunately, 

we meet only once a year to reconnect with our far-flung colleagues to reinvigorate 

and recommit ourselves. I see the RWISO Journal as having a vital function 

in sharing information for those members who attend the annual meeting and, more 

importantly, for those who cannot. It gives us something to hand to our non-Roth 

Williams orthodontists and dental colleges to show the type of research and clinical 

results that is being produced. The articles is this issue are diverse and some are 

groundbreaking. 

You will note this issue of the Journal is mostly articles with only one case report. 

Oddly, we have had very few case reports submitted. My feeling is that the RWISO 

Journal needs a better balance of articles and case reports. Over the years I have seen 

many outstanding cases presented at the RWISO meetings. One of the strengths of our 

group has always been in showing well-treated cases with beautiful finishes. However, 

more importantly, these cases have one more thing in common: stable joints with 

good function of the teeth and joints. And how do we know this? We know because 

we evaluate our results with the use of centrically mounted models, condylar recording 

systems, and TMJ scans. I believe it is the documentation of our orthodontic cases 

that defines our group. Any journal can show a pretty orthodontic finish. It is another 

thing to show all the records, the treatment planning, and then the clinical execution 

and a measured outcome of a challenging case. Since this Journal will be seen by many 

non-Roth Williams orthodontists, I think it is critical we show more of our clinical 

orthodontic work in this journal. 

I hope to see this Journal grow and become a vital part of our organization as it is a 

reflection of who we are and what we believe in. 

Thomas Chubb, DDS 

Editor-in-Chief 

tkchubb1@earthlink.net


ARGENTINA 

We are pleased to announce that in May of this year we began the Roth 

Williams FACE (The Foundation for Advanced Continuing Education) 

Course in cooperation with the Catholic University of Argentina. Dr. 

Oscar Palmas, Dr. Guillermo Ochoa and Dr. Eduardo Rubio (surgeon) 

were he instructors for this course. They had the honor of working 

alongside Dr. Domingo Martin and Dr. Jorge Ayala. The highlight was a 

lecture given by Dr. Martin on interdisciplinary treatment. 

Many feeder courses were developed this year in different provinces, 

including Salta, Jujuy, Rio Gallegos and Santiago del Estero. More than 

300 hundred students were taught about the Roth Williams philosophy. 

In September 2011, Dr. Jorge Ayala will give a feeder course 

entitled “Biomechanical Treatment in Roth Philosophy.” 

For next year we are planning a Roth Williams FACE national meeting 

in Jujuy, an Argentinean province. The Roth Williams Center Argentina 

will participate in the Mendoza Society Orthodontic Meeting in 

September. Dr. Oscar Palmas will give a lecture on self-ligation and 

micro-screw in Roth Philosophy. 

We are very happy to see the poster contributions for the Rome meeting 

from our Roth Williams students. We would also like to take this 

opportunity to congratulate the Journal on its second issue. We encourage 

you all to continue working!! 

Dr. Oscar Palmas 

Director, Roth Williams Center Argentina 

BRAZIL 

The Brazilian Center began a new CCO group in June 2009. It has 

attracted students from the northwest to the southwest of Brazil. Dr. 

Fantini has been traveling to various places in Brazil to spread the 

Roth Philosophy. She has been teaching courses and has even lectured 

at an advanced-level specialization course, where her talks about the 

Philosophy have become a tradition. 

In October 2010, the SPO meeting, which is the most important meeting 

in Latin America, will take place in Brazil. Dr. Fantini will speak 

on Roth’s Philosophy: multidisciplinary treatment of skeletal class II 

malocclusion with bilateral condylar degeneration and generalized root 

resorption. 

Since 2009 four abstracts have been published in conference proceedings, 

three articles have been accepted in orthodontic magazines, and 

two book chapters have been dedicated to the Roth Philosophy. Dr. 

Fantini has participated in 10 MA, PhD, and qualifying examinations 

as an examiner, enhancing the concepts of the Roth Philosophy. For a 

complete list of the articles and abstracts, please contact the RWISO 

office. 

The study group founded in the beginning of 2008 remains active with 

reunions every 2 months. We believe we have found an interesting formula 

to deepen the knowledge of those who took the CCOs. At each 

group meeting, our program includes 3 activities—a participant presentation 

on a given theme, a clinical case presentation and discussion, 

and a talk on a new topic of current interest. This format has made the 

study group very popular. 

We plan to start a new CCO group in June 2011. 

Finally, we are considering organizing a memorial meeting for all South 

America in São Paulo in November 2010. 

Dra. Marisa Gianesella Bertolaccini 

Director, Roth Williams Center Brazil 

CHILE 

As is traditional, our educational activities have remained very active 

through continuing courses, 2- or 3-day courses, and participation 

in various meetings. We are currently offering long-term courses in 

Mexico (two), Argentina, Paraguay, and Chile with a total of 170 

students. In 2009 thru 2010 we held 34 courses. 

In 2010 we will offer two new continuing courses, one in Michoacán, 

México, and the other one at the Universidad de Tucumán, Argentina. 

A course in Brazil, to be held in collaboration with Dr. Solange Fantini, 

is also being organized. 

Drs. Jorge Ayala and Gonzalo Gutierrez 

Directors, Roth Williams Center Chile 

JAPAN 

We are pleased to announce that we now have 45 members. Members 

are doctors who have graduated from the 2-year course and have also 

presented cases with stable and repeatable jaw position. Each year we 

hold an annual meeting where each participant shows his/her cases 

treated according to the Roth philosophy. Along with the annual meeting, 

we are now preparing for the 15th anniversary meeting in Tokyo 

on November 28-29. This meeting is open to all interested doctors. 

We are expecting a great attendance. We of course welcome RWISO 

members from all over the world. 

The ninth 2-year course is steadily ongoing and session 5 was held for 

5 days in June, and featured Dr. Jorge Ayala from Chile as a special 

instructor. The 14th basic course will be held in the fall. 

Dr. Kazumi Ikeda 

Director, Roth Williams Center Japan 

continued on next page... 


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KOREA 

In March 2010 the eighth Roth Williams International Seminar was 

held. The 10 participants in the course were instructed by Drs. Byungtaek 

Choi, Eunah Choi, and Gyehyeong Lee. All participants enthusiastically 

took part in the course. 

As visiting professors, Drs. Byungtaek Choi and Eunah Choi lectured 

on the Roth philosophy to the residents of the Department of Orthodontics 

at the Seoul National University Dental Hospital. The lectures 

were held weekly during the month of June 2010. 

The Roth Williams Center Korea has been encouraging our members 

to contribute to the Roth Williams Legacy Fund. We expect a desirable 

outcome by the 2010 annual meeting in Rome. 


Director, Roth Williams Center Korea 

SPAIN 

Without any doubt 2009 was a great year for RW Spain/Portugal. 

Concerning the RW 2-year course, this year we finished group number 

10 (26 students) and we started group number 11 (28 students). The 

2-year course has truly grown to be a comprehensive orthodontic 

course. We now have three full-time teachers who come to every 

session and not only help in the clinic but also present as teachers. 

They are Drs. Alberto Canabez from Barcelona, Eugenio Martins 

from Portugal, and Iñigo Gomez from Bilbao. All three of them have 

contributed to the excellent quality of the RW course. Apart from these 

full-time teachers, we have also incorporated into our courses experts 

in the different fields of dentistry, who have come and taught different 

sessions. They are Dr. Iñaki Gamborena, prosthodontist, Drs. Jon 

Zabalegui and Iñigo Sada, periodontists, Dr. Dave Hatcher, radiologist, 

Dr. Borja Zabalegui, endodontist, Dr. Renato Cocconi, orthodontist, 

and Dr. Mirco Raffaini, surgeon. All of these teachers have given the 

RW courses a truly interdisciplinary approach, which is what FACE 

promotes worldwide. 

Another important aspect of 2009 that has been fundamental in 

making RW a truly interdisciplinary course is the fact that we have 

organized two different courses, Bioesthetics with Dr. Ken Hunt and Dr 

Alejandro James, and Orthognathic Surgery with Dr. Lucho Quevedo. 

Many of our former students have signed up for the courses, and this 

has given them a greater understanding of the importance of incorporating 

both disciplines into our interdisciplinary approach. But we 

cannot forget that with Osteoplac now organizing and promoting our 

courses they have become truly professional, and without this support 

we could have never reached the status that we now enjoy. 

Dr. Domingo Martín 

Director, Roth Williams Center Spain and Portugal 

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UNITED STATES 

New and exciting things are happening within the Advanced Education 

in Orthodontics (AEO) group. In June of 2010, Group VIII will 

have their graduation. Group VIII is the largest class, with 25 doctors. 

A total of 125 doctors have finished the rigorous seven sessions. The 

directors have been extremely uplifted by the positive responses given 

by the graduates as to their overall educational experience. Comments 

like this are the usual: “Keep up the good work. I thank you daily in 

the back of my mind for telling me I needed to take this course and 

that I would be a better orthodontist. You guys were absolutely right 

and as challenging as our profession is and as smart as our colleagues 

are, I feel light years ahead of them and my GP’s thank you.” Ben. 

The course is continuing to improve and evolve without sacrificing any 

of the Roth Williams basics. Techniques such as the true horizontal 

hinge axis mountings combined with true horizontal hinge axis 3-D 

imaging have been introduced to improve accuracy of diagnosis and 

treatment planning. In the past, AEO was successful in improving the 

Visual Treatment Options (VTO) both in ease of use and in teaching 

technique. Now the course incorporates the latest in 3-D technology. 

The directors have been instrumental in developing software that enhances 

the efficiency of orthodontic diagnosis and treatment planning. 

The next step is to develop 3-D software that is based on the true hinge 

axis. This is being handled by Dr. Robert Frantz. 

Dr. Andrew Girardot is responsible for editing and publishing the longawaited 

Roth Williams Philosophy textbook. Because of the substantial 

commitment required for this important project, Andy will not be 

teaching formally until his work on the book is complete. 

The true standard wide archform (SWA) system that Dr. Roth developed 

is continuing to evolve. With the help of the Head of Product Development 

at GAC, Tom Macari, and AEO, improvements to the bracket are 

in the works. 

The teaching techniques developed at AEO are evolving as well. With 

the advent of new computer technology, many new and exciting things 

will be happening in the next year. 

The Roth Williams USA center has a new home base. Due to an excellent 

opportunity afforded us by Dr. Carlos Navarro, AEO will be moving 

to Houston, Texas. So in October of 2010, Group IX will travel to 

Texas for the new class. The new facility will have adequate space for 

teaching the total Roth Williams experience. The clinical, laboratory, 

and lecture will now be in one location. This location is close to many 

fine restaurants and entertainment. 

Drs. Andy Girardot, Bob Frantz, and Ted Freeland 

Directors, Roth Williams Center USA 

URUGUAY 

Once again, it is a pleasure for the Roth Williams Center Uruguay for 

Functional Occlusion (RWCUFO) to be present in our Journal. 

We would like to inform you that finally in December 2009, our 3-year 

course started in the Faculty of Odontology, Catholic University of 

Montevideo, Uruguay. The first three sessions have been completed, with 

a total of 13 participants. We are having real success with the contributions 

of our friends and outstanding speakers from all over the world.

In addition, three 8-hour courses were scheduled in April, August, 

and December 2010. Presentations include Dr. Roth’s Philosophy: the 

importance of the condyle setting in the fossae:physiological principles 

for neuromuscular deprogramming, by Dr. Guillermo Ochoa; Treatment 

planning according to Roth’s Philosophy, by Dr. Oscar Palmas; 

and Evidence-based Roth’s Philosophy and its application in multidisciplinary 

treatments, by Dr. Domingo Martín. Dr. Martín will also be 

giving a 4-day course for all the specialists related to orthodontics. 

To know more about our courses, please visit the Web page www.ucu. 

edu.uy/Odontologia, or contact us by e-mail at rwcuruguay@gmail. 

com. 

Our group is concerned about research. To address this concern, we 

are encouraging our students to make a weekly commitment to our 

study group. We are working hard in order to achieve the best results. 

Dr. Daniela Domínguez Di Prisco 

Director, Roth Williams Center Uruguay 

Scenes from RWISO 2009 

16th Annual Conference, Boston, MA 


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The Roth Williams Legacy Fund Committee Report 

Dr. Milton D. Berkman, Chairman, RWLF 

Dr. Milton D. Berkman, 

Chairman RWLF 

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Roth Williams Legacy Fund 

Fund-Raising Progress 

As of June 1, 2010, $208,650 had been donated to the Roth Williams Legacy Fund (RWLF). 

Of the money donated, $178,650 has been given to the general research and education portion 

of the fund and $30,000 has been specifically donated to the Roth Williams textbook portion 

of the fund. 

As of June 1, 2010, $107,290 had been pledged to RWLF but had not yet been donated. 

RWLF is proud of the progress that has been made to date. Due in part to the worldwide 

economic recession, we realize that our campaign goal of $1 million in 5 years may not be 

attainable. However, we truly believe that the goal of $1 million will be reached as RWISO 

continues to grow in stature and respect. The future is bright for the Roth Williams Philosophy 

of goal-directed interdisciplinary patient care. 

A special thanks to Drs. Jeff McClendon and Milt Berkman for giving the Coordinating Orthodontic and Restorative Efforts 

(CORE) course and raising almost $9,000 for RWLF. As of July 2010, the course will have been given four times. 

2009 Boston Meeting and Journal 

At the RWISO International meeting held in Boston, Massachusetts, in May 2009, the Committee was pleased with the 

membership’s response to the RWLF fund-raising campaign for the general endowment fund and for the Roth Williams 

Philosophy textbook fund. The publication of the first issue of the RWISO Journal, in May 2009, came to fruition in part 

because of a grant from the RWLF general endowment fund for $14,000. As Dr. Domingo Martín said in the first issue of 

the Journal, “I cannot forget it was Dra. Anka Sapunar who first founded a journal for this group, and we must all be very 

grateful to her for the great job that she did. This is a continuation of what she started. Muchas gracias, Anka!!!” 

The renewal of the Journal would not have been possible without the seed money from RWLF. This is just one of the many 

ways that RWLF is able to fulfill its mission to advance the scientific and clinical benefits of the Roth Williams Philosophy 

of goal-directed interdisciplinary patient care. What a great moment for the RWISO membership! For RWLF it was a significant 

first step, because it demonstrated the important role of an endowment fund in the future growth and longevity of an 

organization and a philosophy of patient care. RWLF and the RWISO membership are looking forward to the second issue 

of the RWISO Journal at the Rome Conference with great anticipation. 

Research Evaluation and Approval Committee (REAC) 

The RWLF Committee’s initial major efforts have been directed toward fund-raising, and toward gaining the trust and 

confidence of the RWISO membership. Now that 30% of the $1 million goal has been pledged or donated, the Committee 

is ready for a new endeavor—to develop research grant evaluation, approval, and funding. One of the mission 

statements of RWLF is “partial or full support of research projects that lead to publication of scientific and clinical 

papers in peer-reviewed international journals.” The Committee is pleased to announce that two research grants have 

been approved and are in the process of being funded by RWISO/RWLF.

Drs. Edson Illipronti and Solange Fantini from Brazil were awarded a grant for a research project entitled Evaluation 

of functional morphology in children with unilateral posterior crossbite before and after rapid maxillary expansion. 

The grant is to pay in part for MRI studies. The grant is for $16,000 over a 3-year period. 

Drs. Carol Weinstein and Sigal Bentolila Weiner from Chile were awarded a grant for a research project entitled Degree 

of apical root proximity, periodontitis, and root resorption of the upper canine and first bicuspid found in sample 

of Roth prescription-treated orthodontic cases using cone beam radiography compared to panoramic radiography. 

The grant is to pay in part for cone beam radiography studies. The grant is for $3,000 over a 3-year period. 

Donation and Pledges 

Donations to RWLF can be made in the following ways: 

1. Professional Courtesy/Grateful Patient. Persons to whom you offer orthodontic services as a courtesy are invited to 

demonstrate their appreciation by making a contribution to RWLF in your name. 

2. Case for the Future of the Roth Williams Philosophy. Doctors can donate one new case as a “case for the future” 

by paying the fee to RWLF. 

3. Doctors giving courses or lectures can donate a portion of the honorarium or course fees to RWLF. 

4. Donations can be made in memory of, or in honor of, a colleague, friend, relative, or parent. 

5. Or just make a donation because of what the Roth Williams Philosophy has meant to your professional life 

Donations can be designated for the general research and education fund or for publication of the Roth Williams 

Philosophy textbook. 

For more on how to donate, visit the RWISO Web site at www.rwiso.org. 

RWLF Committee 

Thank you to those individuals who serve on the Legacy Fund Committee. 

Milton D. Berkman, Chairman RWLF 

Peggy Brazones 

Alan Marcus 

Domingo Martín 

Jeff Milde, Executive Director RWISO 

Joe Pelle 

Straty Righellis, Chairman REAC 

Manny Wasserman 

David Way 


9

Roth Williams Legacy Fund Donors 

Tribute to Donors 

We thank all of our loyal and faithful donors for their support of the Legacy Fund. Below, we pay tribute to those donors who have given from 

January 1, 2006, through June 21, 2010. 

Platinum (10,000 - $49,999) 

Dr. Milton D. Berkman 

Dr. Domingo Martin 

Dr. Straty Righellis 

Dr. Carl Roy 

Dr. Manny Wasserman 

Dr. Robert E. Williams 

Gold Circle ($5,000 - $9,999) 

Dr. Margaret Brazones 

Dr. Byungtaek Choi 

Dr. Andrew Girardot 

Dr. Darrell Havener 

Dr. John Lawson 

Dr. Jina Linton 

Dr. Jeffrey McClendon 

Dr. James Sieberth 

Dr. Wayne Sletten 

Dr. David Way 

GAC International 

Silver Circle ($1,000 - $4,999) 

Dr. Terry Adams 

Dr. Claudia Aichinger 

Dr. Robert Angorn 

Dr. Joachim Bauer 

Dr. Patricia Boice 


Dr. Frank Cordray 

Dr. K. George Elassal 

Dr. Keenman Feng 

Dr. Michael Goldman 

Dr. Frank Gruber 

Dr. David Hatcher 

Dr. Kazumi Ikeda 

Dr. John Kharouf 

Dr. L. Douglas Knight 

Dr. Young Jun Lee 

Dr. Gerald Malovos 

Dr. Alan Marcus 

Dr. Ramon Marti 

Dr. Roger Pitl 

Dr. Paul Rigali 

Dr. Nile Scott 

Dr. Sean Smith 

Dr. Katsuji Tanaka 

Reliance Orthodontic Products 

10 Legacy Fund Donors 

Bronze Circle ($1 - $999) 

Dr. Hideaki Aoki 

Dr. George Babyak 

Dr. Mary Burns 

Dr. Dara Chira 

Dr. Tom Chubb 

Dr. Warren Creed 

Dr. Graciela de Bardeci 

Dr. Chieko Himeno 

Dr. Takehiro Hirano 

Dr. Akira Kawamura 

Dr. Mi Hee Kim 

Dr. Yutaka Kitahara 

Dr. Shunji Kitazono 

Dr. Felix Lazaro 

Dr. N. Summer Lerch 

Dr. Ilya Lipkin 

Dr. George Marse 

Jeff Milde 

Dr. Kouichi Misaki 

Dr. Hideaki Miyata 

Dr. Yo Mukai 

Dr. Yoshihiro Nakajima 

Dr. Joseph Pelle 

Dr. Akiyuki Sakai 

Dr. Atsuyo Sakai 

Dr. Hidetoshi Shirai 

Dr. Motoyasu Taguchi 

Dr. Naoyuki Takahashi 

Dr. Hiroshi Takeshita 

Dr. Yasoo Watanabe 

Dr. Benson Wong 

Dr. Koji Yasuda 

Dr. Yeong-Charng Yen 

Estate Planning 

Dr. Charles R. de Lorimier 

Dr. Donald W. Linck, II 

Friends of Roth Williams 

Advanced Education in Orthodontics 

Jewish Communal Fund 

T&T Design Lab (Japan) 

Timothy McCarthy 

Pledge Circle 

Thank you to these donors who have pledged 

donations to the Legacy Fund over multiple years. 

Dr. Satoshi Adachi 

Dr. Scott Anderson 

Dr. Jorge Ayala 

Dr. Milton Berkman 

Dr. Margaret Brazones 

Dr. Warren Creed 

Dr. Robert Good 

Dr. Mila Gregor 

Dr. Tateshi Hiraki 

Dr. Maria Karpov 

Dr. Mi Hee Kim 

Dr. Masako Komatsu 

Dr. Jina Lee Linton 

Dr. Ilya Lipkin 

Dr. Dave Livingston 

Dr. Yuci Ma 

Dr. Alan Marcus 

Dr. Ramon Marti 

Dr. Joseph M. Pelle 

Dr. Paul Rigali 

Dr. Nile Scott 

Dr. Wayne Sletten 

Dr. Manny Wasserman 

Dr. Benson Wong 

Dr. Yeong-Charng Yen 

Dr. Michael Yitschaky

The Transverse Dimension: 

Diagnosis and Relevance to Functional Occlusion 

Ryan K. Tamburrino, DMD ■ Normand S. Boucher, DDS ■ Robert L. Vanarsdall, DDS 

■ Antonino G. Secchi, DMD, MS 

Ry a n K. Ta m b u R R i n o , DMD 

rktambur@dental.upenn.edu 

■ Clinical Associate—Univ. of Penn. 

School of Dental Medicine, Dept. 

of Orthodontics 

noR m a n d S. bo u c h e R, ddS 

■ Clinical Associate Professor— 

Univ. of Penn. School of Dental 

Medicine, Dept. of Orthodontics 

Rob e R T L. Va n a R S d a L L , ddS 

■ Professor and Chair— 

Univ. of Penn. School of Dental 

Medicine, Dept. of Orthodontics 

anT o n i n o G. Se c c h i , DMD, MS 

■ Assistant Professor of Orthodontics, 

Clinician Educatorand Clinical 

Director—Univ. of Penn. School of 

Dental Medicine, Dept. of Orthodontics 

For complete contributor information, please see end of article. 

Introduction 

The goals of orthodontic treatment are well established 

for static and functional occlusal relationships. In order 

to achieve Andrews’ six keys to normal occlusion for the 

dentition, 1 the jaws must be optimally proportioned in 

three planes of space and positioned in CR. Orthodontists 

have a multitude of cephalometric analyses available to diagnose 

skeletal and dental variations of the sagittal and 

vertical dimensions. 2–6 Several analyses for the transverse 

dimension are also available, 3,6,7 but these analyses are not 

well accepted as forming part of a traditional orthodontic 

diagnosis. 

In the sagittal dimension, when the jaws do not relate 

optimally, the dentition will attempt to compensate, resulting 

in excessively proclined or retroclined anterior teeth. In the 

transverse dimension, when the jaws do not relate optimally, 

usually due to a deficiency in the width of the maxilla, 7,8 the 

teeth will erupt into a crossbite or reconfigure their inclinations 

to avoid a crossbite. This compensation typically 

involves lingual tipping of the mandibular posterior teeth, 

which are then described as being excessively negatively inclined. 

In addition, the maxillary posterior teeth are tipped 

Summary 

Much focus of orthodontic diagnoses has been placed on the sagittal and vertical 

dimensions. However, a proper evaluation of the transverse dimension 

must also have equal importance. Research has shown that interferences from 

an exaggerated curve of Wilson due to a maxillary transverse deficiency play 

a role in centric relation (CR)/central occlusion (CO) discrepancies, adverse 

periodontal stresses, and craniofacial development. This article illustrates 

three scientifically validated methods for evaluating the transverse dimension: 

Ricketts’ P-A cephalometric analysis, Andrews’ Element III analysis, and the 

University of Pennsylvania Cone-Beam CT transverse analysis. The aim is to 

show methods using traditional cephalometry, study models, and cone-beam 

computed tomography, not to compare one method to another. The reader 

may then choose to use the method that is most appropriate for his practice. 

facially. These teeth are then described as being excessively 

positively inclined (Figure 1). 

Figure 1 Example of excessive tooth angulations. 

Transverse Deficiency and CR/CO Discrepancy 

In the prosthodontic literature, these transverse tooth compensations 

have been graphically illustrated with a crossarch 

arc constructed through the buccal and palatal cusps of 


11

the maxillary molars. This is known as the curve of Wilson. 

With excessive inclination of the maxillary molars to compensate 

for insufficient maxillary width, the curve of Wilson 

is greatly exaggerated, and the palatal cusps are positioned 

below the buccal cusps (Figure 2). 

Figure 2 An exaggerated curve of Wilson 

(note palatal cusps below buccal cusps). 

Many articles that describe the impact of CR/CO discrepancies 

on occlusion focus on how these discrepancies 

affect diagnosing the sagittal and vertical dimensions. The 

literature has suggested that the “plunging” palatal cusps 

shown in Figure 3 are often the primary contacts that induce 

vertical condylar distraction on closure from CR. From 

a seated condylar position, the patient may fulcrum off the 

premature contacts of the terminal molars to obtain the 

maximal intercuspal position. The Panadent Condylar Position 

Indicator (CPI) and the SAM Mandibular Position Indicator 

(MPI) graphically identify this vertical component of 

condylar distraction. 9-12 

Figure 3 Note plunging palatal cusps and extreme curve 

of Wilson on molars of an arch that was expanded 

with arch wires and brackets only. 

12 Tamburrino et al | The Transverse Dimension: Diagnosis and Relevance to Functional Occlusion 

According to McNamara and Brudon, 13 “the orientation of 

the lingual cusps of the maxillary posterior teeth… often lie[s] 

below the occlusal plane… This common finding in patients 

with malocclusions often is due to maxillary constriction and 

subsequent dentoalveolar compensation in which the maxillary 

posterior teeth are in a slightly flared orientation.” The results 

of a study by McMurphy and Secchi14 indicate that vertical distraction 

of the condyles in CR/CO discrepancies can be related 

to an exaggerated curve of Wilson, secondary to a transverse 

deficiency of the maxilla. These authors conclude that, in the 

absence of a posterior crossbite, the plunging palatal cusps and 

exaggerated curve of Wilson become the fulcrum point for the 

vertical condylar distraction from CR to maximum intercuspation. 

Furthermore, extrapolation of this statement suggests that 

if the transverse skeletal dimension is normalized, the curve of 

Wilson is flattened, and the arches are coordinated, an important 

component of the CR/CO discrepancy is eliminated. 

Transverse Deficiency and Working/Nonworking 

Interferences 

It has been a prosthetic maxim that an exaggerated curve of 

Wilson increases the potential for working and non-working 

side interferences. Studies have shown that posterior occlusal 

contacts or interferences are linked to increased masticatory 

muscle activity. 15,16 In studies where these interferences have 

been removed, it has been demonstrated that the activity of the 

closing musculature is reduced. 16,17 In addition, a study that artificially 

created non-working interferences reported increased 

muscle activity. 18 These results suggest that it is prudent to normalize 

the transverse jaw relationship and flatten the curve of 

Wilson to eliminate the potential for excursive posterior interferences 

or contacts. 

Transverse Deficiency and the Periodontium 

Herberger and Vanarsdall19 have shown an increased risk for 

gingival recession in the orthodontic patient with a narrow 

maxilla when the skeletal transverse deficiency is camouflaged 

with dental expansion. The envelope of treatment in the transverse, 

with expansion of only the dentition, is more limited than 

the envelope of treatment in the sagittal dimension. 20 Due to the 

constraints of the thin layer of cortical bone of the alveolus, as 

shown in Figure 4 [see next page], very little tooth movement 

needs to occur before the roots are fenestrated, the volume of 

buccal alveolar bone is reduced, and, with thinning gingival tissues, 

the risk of gingival recession increases. 

In recent studies, Harrell21 and Nunn and Harrell22,23 have 

shown that the elimination of working and nonworking interferences 

enhances the long-term periodontal prognosis in patients 

susceptible to periodontal disease. Therefore, normalizing the 

transverse jaw relationship to eliminate an exaggerated curve

Figure 4 Patient with gingival recession due to orthodontic 

treatment in the presence of an undiagnosed severe skeletal 

transverse discrepancy. Note minimal alveolar bone on 

the buccal surface of the maxillary molars. 

of Wilson and nonworking interferences would be beneficial 

for adult patients who are periodontally at risk, and might 

prophylactically reduce the risk for younger patients. 

Transverse Deficiency and the Airway 

Ricketts’ description of “adenoid facies” 24 also suggests a relationship 

between a constricted nasopharyngeal airway and 

a narrow maxilla. Ricketts states children with any impairment 

of the nasal passages become predominantly mouth 

breathers. Since the tongue is positioned in the floor of the 

mouth to allow airflow, it cannot provide support to shape 

the developing palate; thus pressure from the circumoral 

musculature acts unopposed. The palate is narrowed, and 

an exaggerated curve of Wilson develops upon tooth eruption. 

Because the tongue is positioned low in the mouth, the 

patient may also develop a retruded, high-angle mandibular 

shape, which can increase the risk for sleep apnea. 25 An example 

of adenoid facies is shown in Figure 5. 

Figure 5 A teenager who had nasopharyngeal airway impairment 

during growth and development. The images show the facial, 

dental, skeletal, and airway presentation upon growth cessation. 

In one recent study, 26 patients with transverse deficien- 

cies due to a narrow maxilla who were treated with rapid 

palatal expansion, showed an increase of 8% to 10% in the 

volume of the upper airway. In another study, 27 patients with 

dental posterior crossbites who were treated with palatal expansion 

also showed an increase in the volume of the upper 

airway. Oliveria de Felippe, et al28 found that palatal expansion 

decreased nasal resistance and improved nasal breathing. 

While additional research in this area is certainly needed, 

the current literature suggests that any improvement in the 

volume of the airway, as an effect of palatal expansion to 

optimize the transverse dimension of the jaws, may greatly 

benefit overall growth and development. 

Methods of Transverse Diagnosis 

With a transverse deficiency due to a narrow maxilla, the 

temporomandibular joints, musculature, periodontal tissue, 

and airway can be adversely affected in the susceptible patient. 

Our goal as orthodontists should be to develop skeletal 

relationships and a functional occlusion that are as close to 

optimal as possible, to lessen the role that any discrepancies 

of the occlusion would play in exacerbating the detrimental 

effects to the joints, periodontium, or dentition. In order 

to achieve this a correct skeletal and dental diagnosis in all 

three planes of space is mandatory. 

In this section, we present three different methods for 

diagnosing the transverse dimension—one using traditional 

cephalometry, one using dental casts, and one using conebeam 

CT (computed tomography). We do not endorse any 

one of these methods over the others; our purpose here is 

simply to describe all three methods, so that readers will be 

able to incorporate a transverse skeletal diagnosis into their 

practice, no matter what level of technology is available. 

Regardless of which of these methods one chooses, the doctor 

must keep optimal treatment goals in mind as a rationale for 

normalizing the transverse dimension (Figures 6 and 7). 

Figure 6 Goals for normalizing the transverse dimension. 


13

Figure 7 Rationale for normalizing the transverse dimension. 

Ricketts’ P-A Analysis 

In 1969, Ricketts introduced analysis of the transverse skeletal 

dimension as part of his method of cephalometric diagnosis. 

3 His method uses the frontal, or posteroanterior 

(P-A) cephalogram, and is based on the dimensions of the 

jaws compared to a table of age-adjusted normative values. 

The premise of the analysis is based on locating two skeletal 

points to determine maxillary width and two additional skeletal 

points to determine mandibular width (Figure 8). 

Figure 8 Locations of Mx (green) and Ag (yellow). 

For the maxilla, the jugal point (Mx) is located on the right 

and left sides of the maxillary skeletal base at “the depth 

of the concavity of the lateral maxillary contours, at the 

junction of the maxilla and the zygomatic buttress.” 3 The 

maxillary width is determined by the horizontal distance 

connecting these two points. For the mandible, a similar 

measurement is taken between the two antegonial notches 

(Ag). These notches are located on the right and left sides 

of the mandibular body at the “innermost height of contour 

along the curved outline of the inferior mandibular border, 

below and medial to the gonial angle.” 3 

Once the measurements have been taken, the mandibular 

width (Ag-Ag) is subtracted from the maxillary width (Mx- 

Mx) to get the difference in width between the jaws. Ricketts 

then determined skeletal age-determined normative relationships 

between the maxilla and the mandible (Figure 9). This 

allows the analysis to accommodate growing patients, and 

allows for the differential growth rates and potentials of the 

maxilla and the mandible. 

Figure 9 Table for determining the age-normal 

difference between the maxilla and the mandible. 

In order to determine the skeletal age of a patient, a handwrist 

film is taken and is compared to an atlas of male and 

female skeletal age standards. 29 To determine the amount of 

expansion needed, the age-adjusted expected difference between 

the jaws is subtracted from the measured difference. 

An example of the Ricketts method is shown in Figure 10. 

Figure 10 Example of Ricketts’ P-A analysis. 

Andrews’ Element III Analysis 

In 1970, L. F. Andrews published his landmark paper describing 

the six keys to normal static occlusion. 1 Over the next 

several decades, he and his son, W. A. Andrews, worked to develop 

the six elements philosophy of orthodontic diagnosis. 

One of the diagnostic criteria, Element III, is devoted to analyzing 

the transverse relationship of the maxilla and mandible 

and is based on both bony and dental landmarks. 10 

The Element III analysis is based on the assumption that 

the WALA (named after Will Andrews and Larry Andrews) 

14 Tamburrino et al | The Transverse Dimension: Diagnosis and Relevance to Functional Occlusion

idge determines the width of the mandible. According to 

Andrews’ definition, the WALA ridge is coincident with the 

most prominent portion of the buccal alveolar bone when 

viewed from the occlusal surface (Figure 11). 

Figure 11 Demarcation of the WALA ridge. 

The WALA ridge is essentially coincident with the 

mucogingival junction and approximates the center of resistance 

of the mandibular molars. In a mature patient, 

the WALA ridge and the width of the mandible cannot be 

modified with conventional treatment. Thus the WALA ridge 

forms a stable basis for the Element III analysis. 6 

The Element III analysis is based on the width change, 

if any, of the maxilla needed to have upper and lower posterior 

teeth upright in bone, centered in bone, and properly 

intercuspated. To determine the discrepancy, the first step is 

to determine the width of the mandible, or the horizontal 

distance from the WALA ridge on the right side to the WALA 

ridge on the left side. According to Andrews, optimally positioned 

mandibular molars will be upright in the alveolus, 

and their facial axis (FA) point, or center of the crown, will 

be horizontally positioned 2 mm from the WALA ridge. With 

this information, the width of the mandible is then defined as 

the WALA-WALA distance minus 4 mm. 6 

Figure 12 Determination of mandibular 

WALA-WALA and FA-FA distances. 

The width of the maxilla is based on optimization of the 

angulation of the maxillary molars. To determine this width, 

one measures the horizontal distance from the FA point of 

the left molar to the FA point of the right molar and records 

the measurement. 

Figure 13 Determining maxillary FA-FA distance and 

estimating the change in maxillary molar inclination. 

One then looks at the angulation of the maxillary molars 

and estimates the amount of horizontal change that will 

occur between the FA points of the right and left molars 

when they are optimally angulated. The estimated amount of 

change is subtracted from the original FA-FA measurement. 

The result represents the width of the maxilla. 6 

In order to have optimally positioned and optimally inclined 

molar teeth that intercuspate well, Andrews states that 

the maxillary width must be 5 mm greater than the mandibular 

width. 6 In order to determine the amount of transverse 

discrepancy, or Element III change, needed to produce an 

ideal result, one takes the optimal mandibular width, adds 

5 mm, and subtracts the maxillary width. An example of the 

entire analysis is shown in Figure 14. 

Figure 14 Example of Andrews’ Element III 

transverse analysis. 


15

University of Pennsylvania Cone-Beam CT Analysis 

The current trend in orthodontic imaging and diagnosis is 

toward three-dimensional analysis. With the advent of conebeam 

imaging, orthodontists can obtain precise measurements 

without any distortion caused by radiographic projections 

or ambiguity of point identification. The same rationale 

can subsequently be applied to the transverse measurement 

of the maxilla and the mandible. Ricketts’ and Andrews’ 

methods for determining the amount of transverse discrepancy 

between the jaws are based on using readily discernable 

landmarks that represent the width of the base of the alveolar 

housing. For Ricketts, these landmarks are Mx-Mx for 

the maxilla and Ag-Ag for the mandible. For Andrews, these 

landmarks are the two sides of the WALA ridge and the FA 

points of the maxillary and mandibular molars. The WALA- 

WALA measurement represents the width of the mandible, 

and the FA-FA points are used, as described above, to determine 

the width of the maxilla. Both of these methods have 

merit. However, with cone-beam CT imaging, it is no longer 

necessary to have a measurement dictated by ease with 

which landmarks can be identified to represent the widths 

of the jaws. 

Before choosing a method for measuring the base of the 

jaws, we must first decide what location to use for measurement. 

In determining the location of the WALA ridge, Andrews 

stated that the WALA ridge is an approximation of the 

center of resistance of the mandibular teeth. Above the WALA 

ridge, the alveolus can be dimensionally molded and altered, 

depending on the change in angulation of the teeth. However, 

the same cannot be said for the portion of the alveolus below 

the WALA ridge. Thus, in a mature patient, any portion of the 

alveolus apical to the WALA ridge can be assumed to be reasonably 

dimensionally stable during tooth movement, and, 

therefore, can define the dimensions of the patient’s arch. In 

Ricketts’ analysis, Ag-Ag represents the basal portion of the 

mandible. However, when one looks at the position of Ag on 

a three-dimensional image, one sees that its correlation with 

the base of the alveolus is relatively weak in all three planes 

of space for mature patients (Figure 15). 

16 

Figure 15 Correlations of Mx and Ag to skeletal bases in adults. 

Thus, to locate the beginning of the base of the mandible 

with a CT scan, it would seem best to find the skeletal representation 

of the WALA ridge. This is approximately at the edge of 

the cortical bone opposite the furcation of the mandibular first 

molars. We can also use this technique to locate the beginning of 

the base of the maxilla. If we assume that the maxilla begins at 

the projection of the center of resistance of the maxillary teeth 

onto the buccal surface of the cortical bone, Ricketts’ use of Mx 

to determine maxillary width appears to be at approximately at 

the same horizontal position. Additionally, by using Mx point, 

any exostoses present along the buccal portion of the alveolus 

will not interfere with the measurement. Andrews’ method, 

on the other hand, has no directly definable skeletal landmark 

for the maxilla; it relies on estimated changes in the angulation 

of the molars to determine the skeletal transverse discrepancy. 

Therefore, Ricketts’ method of defining the basal skeletal width 

of the maxilla appears to be more appropriate. 

We begin, then, by defining locations for measuring maxillary 

and mandibular skeletal basal width. Next, we explore 

concepts for defining these locations on cone-beam CT imaging. 

The basic premise for the mandible is to locate the most buccal 

point on the cortical plate opposite the mandibular first molars 

at the level of the center of resistance. According to Katona, this 

location is approximately coincident with the furcation of the 

roots of the molars. 30 As we explained above, the authors chose 

this point due to the relative immutability of the alveolus apical 

to this location with orthodontics and because it represents the 

absolute minimal width of the basal bone for each jaw. 

For the purposes of this technique, the authors used Dolphin 

3D, release 11 (Patterson Dental, Chatsworth, CA), but 

the concepts can be applied to any software with the capability 

to analyze a cone-beam CT image. After properly orienting 

the image, we open the multiplanar view (MPV) screen to see 

simultaneous axial, sagittal, and coronal cuts of the image. 

Tamburrino et al | The Transverse Dimension: Diagnosis and Relevance to Functional Occlusion

Figure 16 MPV of a cone-beam CT scan. 

To determine the width of the mandible, we scroll down 

through the image until we locate the furcation of the first 

molar. Then we scroll posteriorly through the scan until we 

locate the coronal cross-section through the center of the 

mandibular first molars. 

Figure 17 Location of the mandibular axial and coronal cuts. 

Now we switch to full-screen axial view. Using the cut 

lines as a guide, we measure the width of the mandible from 

the intersection of the cut line with the most buccal portion 

of the cortical plate on both the right and left sides. 

Figure 18 Measurement of mandibular skeletal width. 

For the maxilla, a similar method is employed. The only 

difference is that the axial and coronal cuts must be taken at 

the position Mx-Mx, and the same measurement as in the 

Ricketts’ analysis is used. 

Figure 19 Measurement of maxillary axial and coronal cuts. 

Figure 20 Measurement of maxillary skeletal width. 

The analysis of the width of the maxilla and mandible at 

the level of the first molars is straightforward once we have 


17

taken the measurements of both jaws. By subtracting the 

mandibular width from the maxillary width, we determine 

the difference between the two jaws. Both Ricketts’ and Andrews’ 

analyses demonstrate that the optimal transverse difference 

between the maxilla and mandible is 5 mm in mature 

patients. A preliminary analysis of 5 cases where the maxillary 

and mandibular molars were upright in the alveolus, 

centered in the alveolus, and well intercuspated, produced 

measurements where the difference between the width of the 

jaws approximated 5 mm on a consistent basis. Therefore, 

the seemingly ideal difference for the width of the jaws in 

mature patients using the Penn CBCT analysis would also 

appear to be 5 mm. To determine the amount of expansion 

necessary to achieve an ideal jaw relationship in the transverse 

dimension, the measured difference between the jaws 

should be subtracted from 5. 

Figure 21 Example of optimal transverse skeletal 

relationships using cone-beam CT analysis. 

Research performed by Simontacchi-Gbologah, et al31 , 

has verified the validity of the University of Pennsylvania 

CBCT analysis for the transverse diagnosis. However, the 

difference between the described method here and the method 

in the aforementioned research is that the measurements 

were taken on coronal cuts, not axial ones. Due to the cross 

section of the mandibular coronal cut being taken at an angle 

that is not perpendicular to the alveolus, a false perception of 

the thickness of cortical bone is possible, as shown in Figure 

22. Therefore, to reduce errors in judgment and to improve 

visualization of the most buccal portion of the cortical bone, 

the authors believe that the axial cut allows for greater precision 

of measurement over the coronal cross section. 

Figure 22 Visualization of cortical bone thickness 

on coronal and axial cuts of the same patient 

Future Directions 

Now that the methodology of the Penn CBCT analysis has 

been verified, the next goal will be to extrapolate the analysis 

to determine a diagnostic transverse relationship for the canines. 

With this, the goal will be to determine the appropriate 

arch form for proper stability and function on an individual 

basis. An additional study’s aim will be to develop age-specific 

transverse normative criteria for Penn CBCT analysis, 

similar to Ricketts’ norms for the P-A ceph. ■ 

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For complete contributor information, please see next page. 


19

Contributors 

Ryan K. Tamburrino, DMD 

■ Clinical Associate—Univ. of Penn., School of Dental Medicine, 

Dept. of Orthodontics 

■ Andrews Foundation “Six Elements Philosophy” Course—2007 

■ Advanced Education in Orthodontics—Roth-Williams Center 

for Functional Occlusion—2008 

■ University of Pennsylvania, School of Dental Medicine, 

Certificate in Orthodontics—2008 

■ University of Pennsylvania, School of Dental Medicine, DMD 

—2006 

Normand S. Boucher, DDS 

■ McGill University, School of Dental Medicine, DMD, 1974 

■ University of Pennsylvania, School of Dental Medicine, 

Certificates in Orthodontics and Periodontics, 1982 

■ Advanced Education in Orthodontics, Roth-Williams Center 

for Functional Occlusion, 1993 

■ Andrews Foundation, “Six Elements Philosophy” Course, 1998 

■ Clinical Associate Professor, University of Pennsylvania, School 

of Dental Medicine, Department of Orthodontics 

Robert L. Vanarsdall, DDS 

■ Professor and Chair— University of Pennsylvania School of 

Dental Medicine, Department of Orthodontics 

■ DDS—Medical College of Virginia 

■ Certificates in Orthodontics and Periodontics—University of 

Pennsylvania 

■ 80 publications and 11 textbook contributions 

■ Former President of the Philadelphia Society of Orthodontists 

and Eastern Component of the EH Angle Society 

Antonino G. Secchi, DMD, MS 

■ Assistant Professor of Orthodontics-Clinician Educator and 

Clinical Director, Dept. of Orthodontics, University of Penn. 

■ Andrews Foundation “Six Elements Philosophy” Course, USA, 

—2005 

■ Institute for Comprehensive Oral Diagnosis and Rehabilitation, 

OBI Level III—2005 

■ Advanced Education in Orthodontics—Roth/Williams Center 

for Functional Occlusion USA—2005 

■ University of Pennsylvania, MS in Oral Biology—2005 

■ University of Pennsylvania, DMD—2005 

■ University of Pennsylvania, Certificate in Orthodontics—2003 

■ University of Chile—Chile, Certificate in Occlusion, 1998 

■ University of Valparaiso—Chile, DDS, 1996 


Hinge Axis: The Need for Accuracy in Precision Mounting 

Part 2 

Byungtaek Choi, DDS, MS, PhD 

byu n G T a e K ch o i , ddS, mS, Phd 

joydog@unitel.co.kr 

■ Graduated from Seoul National 

University, College of Dentistry 

(DDS), Seoul, Korea, 1981 



(MS), Seoul, Korea, 1984 



(PhD), Seoul, Korea, 1990 

■ Private Practice, Seoul, Korea 

■ Chairman of Korean Foundation of 

Gnatho-Orthodontic Research 

■ Director of Roth Williams Center, 

Korea 

■ Attending Professor of Medical 

School of Hanlim University 

■ Attending Professor at Seoul 

National University 

The Axi-Path System 

Many clinicians use the Panadent Axi-Path system for the 

following purposes: (Figure 17) 

• To locate the true hinge axis (THA) 

• To determine the sagittal anterior condylar path inclination, 

non-working-side sagittal lateral condylar 

path inclination, and the Bennett movement to 

select the Motion Analog Blocks 

• To assess the functional structural conditions of the 

temporomandibular joint 

Figure 17 Axi-Path recording: Panadent Company. 

The upper head frame of the Axi-Path recorder is composed 

of two symmetrical arms that move around a hinge 

joint at the center of the frame (Figure 18). The upper frame 

is fitted and fastened to the head by tightening the hinge with 

Summary 

This is the second part of a two-part paper discussing the need for accuracy 

in the mounting of dental models for orthodontic diagnosis and treatment. 

Part 1 discussed the accuracy differences between an arbitrary hinge axis 

(AHA) mounting and a true hinge axis (THA) mounting. Part 2 discusses the 

differences between two popular true hinge axis recording devices, the Panadent 

Axi-Path system and the Axiograph III system. 

a thumbscrew. A straight ruler can be used to make the two 

flag tables parallel to each other. (Figure 19). 

Figure 18 Head frame (upper frame). 


21

Figure 19 Flag tables are set to be parallel to each other. 

The lower head frame of the Axi-Path recorder is at- 

tached to the lower jaw with the use of a clutch. Two side 

arms which hold the styli are attached to the cross rod to 

record the mandibular movement (Figure 20). 

Figure 20 Lower frame for adjustable axis-locating arms. 

To place the Axi-Path recorder correctly, the upper 

frame is first fitted and fastened to the head. The lower frame 

is then attached to the lower jaw. Finally, the axis-locating 

arms are attached to the lower jaw (Figure 21). 

Figure 21-a The upper frame is placed and fastened to the head. 

Figure 21-b Axis-locating arms are attached to the lower jaw. 

Figure 22 is the schematic drawing of the head viewed 

from the top when the Axi-Path recorder has been placed on 

the head correctly. 

22 Choi | Hinge Axis: The Need for Accuracy in Precision Mounting Part 2 

Figure 22 Schematic drawing of the head viewed from the 

top when the Axi-Path recorder has been placed on the head. 

Figure 23 Asymmetrical head configuration. 

If the patient’s head configuration is asymmetrical, the 

face-bow may not be centered on the head when the nasion 

relator is placed on Nasion (Figure 23). Since the nasion relator 

cannot move transversely, the face-bow should be rotated 

until the nasion relator sits on Nasion (Figure 24). When the 

lower frame is placed, the stylus may not be perpendicular

to the flag table (Figure 25). The Axi-Path is not a collinear 

system, and errors often occur when the clinician attempts 

to determine the THA. If a recording system is not collinear 

and rectilinear, the clinician is likely to mark the inaccurate 

hinge points on the skin. 

Figure 24 Nasion relator cannot 

move along the horizontal part of the bow. 

Figure 25 When the lower frame is placed, the 

stylus may not be perpendicular to the flag table. 

The following experiment can be used to determine the 

magnitude of measurement error. The experiment is set up so 

that the measurement shows the right condyle 5 mm forward 

of its actual position. For purposes of illustration, the situation 

is assumed to be noncollinear (Figure 26). 

Figure 26 Supposition. Right condyle moved 5 mm forward. 

The new hinge axis diverges from the original hinge axis 

as it goes farther from the anatomic structure (Figure 27). 

Figure 27 New hinge axis passing through 

newly positioned condyle. 

The right recording stylus is placed at the new hinge 

point on the flag table (Figure 28). 


23

Figure 28 Stylus placed at the new 

hinge point on the flag table. 

A hinge axis is not a line that connects the centers of the 

condyles. It is the axis around which the mandible shows 

pure hinge movement. Therefore, the hinge axis may pass 

through any point in the condyle. In Figure 29, the center 

points have been marked for clarity. Figure 30 is a magnified 

view of the right joint area. 

Figure 29 

Right condyle 5 mm 

anterior to the left 

condyle. 

Figure 30 Magnified view of the right joint area. 


The example assumes that the distance between the 

centers of the two condyles is 110 mm, and the distance at 

skin level is 140 mm (Figure 31). If the condyle moves 5 mm 

forward, it will appear to move slightly more on the graph 

(Figure 32). If the condyle moves 5 mm forward, the hinge 

point on the skin moves 5.68 mm forward (Figure 33). 

Figure 31 The supposition is that the distance 

between the centers of the two condyles is 110 mm, 

and the distance at the skin level is 140 mm. 

Figure 32 If the condyle moves 5 mm forward, 

it will appear to move slightly more on the graph. 


the hinge point on the skin moves 5.68 mm forward.

The Axi-Path is designed so that the flag table is very 

close to the preauricular skin. For some patients, depending 

on the configuration of the temporal region, the flag table 

may be farther from the skin. Figure 34 shows 5 mm of distance 

between the skin and the flag table. 

Figure 34 Axi-Path is designed so that the flag table is 

very close to the preauricular skin. This picture shows 

5 mm of distance between the skin and the flag table. 

If the distance from where the stylus contacts the flag 

table to the skin is 5 mm, the measurement error will be 0.23 

mm. The amount of error will decrease as the stylus gets 

closer to the skin. The Axi-Path system uses the skin mark 

for face-bow transfer. Hence, the smaller the error, the more 

accurate the hinge axis. Accuracy depends on the distance 

between the flag table and the skin (Figure 35). 

Figure 35 If the distance from the stylus to the skin is 5 mm, 

the amount of error is calculated as follows: 

5.68 : 125 = X : 5 mm (X = 284 ÷ 125 = 0.23 mm) 

The Axi-Path system has some advantages. Because the 

flag table is very close to the skin, measurement error can be 

minimized (Figure 36). And the reference tattoo on the skin 

can be used for precision mounting at any time, once it has 

been marked (Figure37). 

Figure 36 Advantages of Axi-Path system: 

Proximity of the flag table to the skin. 

Figure 37 Advantages of Axi-Path system: 

Proximity of the flag table to the skin. 

However, the Axi-Path system also has shortcomings. 

The head frame often cannot be fastened tightly to the head. 

It is somewhat unstable compared to the frame of the Axiograph 

III. An unstable frame can make it difficult or impossible 

to get a reproducible reference point and may be 

misdiagnosed as an unstable joint (Figure 38). 

Figure 38 Shortcomings of Axi-Path system: 

Unstable head frame. 


25

Since the nasion relator is not movable transversely on 

the face-bow, it is difficult to center the midline of the bow 

perpendicular to the hinge axis in asymmetrical cases. If we 

attempt to do so, the face-bow will be seated off center (Figure 

39). 

Figure 39 Shortcomings of Axi-Path system: 

Off-center placement of the upper frame in asymmetrical cases. 

In short, the Axi-Path system records the hinge axis on a 

flag table that is relatively close to the skin. If the flag table is 

close to the skin, it produces a more accurate hinge mark on 

the skin. However, the primary disadvantages of this system 

are the structural instability of the head frame when fastened 

to the head and the off-centered seating of the face-bow on 

the asymmetrical head. 


The Axiograph III System 

The Axiograph III system is shown in Figure 41. Orthodontists 

use this system for the same purposes as the Axi-Path 

system. The Axiograph III system differs from the Axi-Path 

system in several important ways. 

Figure 41 Axiograph III: SAM. 

Figure 42 is a schematic drawing of the head viewed 

from the top when the upper frame of the Axiograph III has 

been placed on the head correctly. If the patient’s head is 

symmetrical, every part of the frame will be parallel or perpendicular 

to the sagittal plane of the head. 

Figure 42 Schematic drawing and real picture of upper frame. 

This system is collinear and rectilinear. Since the nasion 

relator moves transversely, the upper frame can be placed 

on the head without losing the parallelism, even when the 

patient’s head is asymmetrical (Figure 43). 

Figure 44 shows the upper and lower frames placed on 

the head. The lower frame has two side arms, with a stylus 

on the end of each arm. The two styli are in collinear alignment, 

rectilinear with the upper Axiomatic flag-bow recording 

plates (Figure 45).

Figure 43 Nasion relator moves transversely along 

the horizontal part of frame so the frame can be 

placed on the head without losing parallelism. 

Figure 44 Upper and lower frames 

that have been placed on the head. 

Figure 45 Axiograph III uses two recording styli in a 

collinear alignment, rectilinear with the upper 

Axiomatic flag-bow recording plates. 

The upper frame is fastened to the head first, and the 

lower frame is placed next. If earplugs are inserted into the 

auditory canals, the alignment pins automatically indicate 

the approximate hinge positions. The alignment pins also 

make the upper and lower parts of the face-bow parallel and 

perpendicular to each other (Figure 46). 

Figure 46 If ear plugs are inserted into auditory canals, 

alignment pins automatically indicate approximate hinge 

positions. The alignment pins also make the upper and lower 

parts of the face-bow parallel and perpendicular to each other. 

As was done in the Axi-Path experiment, the amount of 

measurement error is then determined when the right condyle 

is moved 5 mm forward (Figure 47). This movement 

produces a new hinge axis, which in turn makes new hinge 

points on the skin. The new hinge axis diverges from the 

original hinge axis as it moves farther from the anatomic 

structure (Figure 48). 

Figure 47 Supposition: Right condyle moved 5 mm forward. 


27

Figure 48 New hinge axis passing 

through newly positioned condyle. 

Figure 49 is a magnified view of the right joint area. 

Right condyle 5 mm 

anterior to the left 

condyle. 

Figure 49 The supposition is that the distance between 

the centers of the two condyles is 110 mm, and the 

distance at the skin level is 140 mm. 

The example assumes that the distance between the cen- 

ters of the two condyles is 110 mm, and that the distance at 

skin level is 140 mm. If the condyle moves 5 mm forward, it 

will appear to move slightly more on the graph (Figure 50). 

The recording stylus will point to the new hinge on the 

flag table (Figure 51). 

If the condyle moves 5 mm forward, the hinge point on 

the skin will move 5.68 mm forward (Figure 52). 



it will appear to move slightly more on the graph. 

Figure 51 The recording styli will point 

to the new hinge on the flag table. 

Figure 52 IIf the condyle moves 5 mm forward, 

the hinge point on the skin will move 5.68 forward. 

The distance between the skin and the graph table 

is usually greater in Axiograph III than in Axi-Path. 

Taking this into account, the distance between the 

skin and the graph was set at 8 mm in Axiograph III, 

instead of 5 mm, as in Axi-Path.

The distance between the preauricular skin and the flag 

table is usually greater in the Axiograph III than it is in the 

Axi-Path. Taking this into account, the distance between the 

skin and the flag table was set at 8 mm in the Axiograph III. 

When the flag table is 8 mm away from the skin, the measurement 

error will be 0.36 mm. This is 0.13 mm larger than 

the 0.23 mm measurement error with the Axi-Path, which 

has the flag table 5 mm away from the skin (Figure 53). 

Figure 53 If the distance from the stylus to the skin is 8 mm, 

the amount of error will be calculated as follows: 

5.68 : 125 = X : 8 mm (X = 45.4 ÷ 125 = 0.36 mm) 

If we were to transfer the face-bow of the Axiograph III 

system in the same way as we transfer the face-bow of the 

Axi-Path system, we would have to shorten the distance between 

the skin and the flag table to reduce the measurement 

error. However, in the Axiograph III system we use hinge 

marks on the graph, rather than hinge marks on the skin, for 

precision mounting. 

Now let us further suppose that the stylus is placed 50 

mm, rather than 8 mm, away from the skin (Figure 54). 

Figure 54 Supposition: The stylus is 50 mm away from the skin. 

Although this situation is one that we may not encoun- 

ter in practice, it is useful as an example to explain an extreme 

case (Figure 55). 

Figure 55 Magnified view. 

It is obvious that the measurement error becomes larger 

when the distance from the stylus to the skin is 50 mm (Figure 

56). In fact, the measurement error will be 2.3 mm (Figure 57). 

Figure 56 The measurement error becomes larger 

when the distance from the stylus to the skin 

changes from 8 mm to 50 mm. 

Figure 57 If the distance from the stylus to the skin 

is 50 mm, the amount of error will be calculated as follows: 

5.6 8: 125 = X : 50 mm (X = 284 ÷ 125 = 2.3 mm) 


29

This is an extremely large error when we are attempting 

to locate a THA. Fortunately, it seldom happens that we attempt 

to locate a THA from a distance of 50 mm in clinical 

practice (Figure 58). 

Figure 58 If we try to extend the stylus to the skin to mark a 

hinge point from a point located at a far distance from the 

skin using Axiograph III, it would result in a very large error. 

The fact remains, however, that the greater the distance 

between the skin and the stylus, the less accurate are the 

marks on the skin (Figure 59). Therefore, we are likely to 

make a large error if we use a false hinge axis that deviates 

substantially from the THA (Figure 60). 

Figure 59 The greater the distance between the skin 

and the stylus, the less accurate the marks of 

the THA on the skin will be. 

Precision mounting 

using a false hinge 

axis results in a very 

large error. 

Figure 60 We are likely to create a large error if we use the 

false hinge axis, which deviates substantially from the THA. 


Next, let us examine the precision mounting system of 

the Axiograph III. Figure 61 shows a magnified view of the 

highlighted area. The various parts of the highlighted area 

are shown in Figure 62. They are, respectively, the side arm 

of the upper frame, the flag table attached to the side arm, 

the recording arm of the lower frame, and the stylus attached 

to the recording arm. 

Figure 61 Schematic drawing and 

real picture of the stylus area. 

Figure 62 Magnified view 

The THA is the line that connects the left and the right 

styli. It passes through an imaginary hole in the flag table. 

The stylus marks the hinge point in red or blue on the graph 

of the flag table (Figures 63 and 64).

Figure 63 Flag table. 

Figure 64 Flag table. 

The hinge point on the graph is isolated with the hinge 

axis clamp. The hinge axis clamp has two bars. Each bar has 

a hole in it, and the two holes are aligned (Figures 65 and 

66). 

Figure 65 Flag table with hinge axis clamp. 

Figure 66 Schematic drawing and real 

picture of the flag table and the clamp. 

The precision mounting stand has two hinge axis align- 

ment pins. These pins are designed to fit into the small holes 

on the inner bar of the hinge axis clamp (Figures 67-a, b). 

Figure 67-a Hinge axis alignment pin 

fits into the inner clamp hole. 

Figure 67-b Hinge axis alignment belongs to mounting stand. 


31

In this respect, the Axiograph III system differs from 

the Axi-Path system; in the Axi-Path, the stylus of the lower 

frame fits into the female part of the mounting shaft. Therefore, 

we do not need to re-mark the hinge point on the skin 

with the Axiograph III as we do with the Axi-Path. Instead, 

we use the hinge points on the graphs for precision mounting. 

In other words, we treat the graph as if it were the skin 

in the Axiograph III system (Figure 68). 

Figure 68 In Axi-Path, the stylus (axis pin) of the lower frame 

is adapted to the female part of the mounting shaft. In 

Axiograph III, the hinge axis alignment pins of the mounting 

stand are fitted into the small holes on the inner bar of the 

hinge axis clamp. Therefore, we need not re-mark the hinge 

point on the skin, as we do with Axi-Path. Instead, we use 

the hinge points on the graphs for precision mounting. 

The distance from the tip of the hinge axis alignment 

pin to the THA is the measurement error (Figure 69). It is interesting 

to observe that the measurement error increases as 

the flag table moves closer to the skin medially (Figure 70). 

Conversely, the measurement error decreases as the flag table 

moves farther from the skin laterally (Figure 71). 

Figure 69 The distance from the tip of the hinge axis 

alignment pin to the THA is the measurement error. 


Figure 70 Measurement error increases as the 

flag table moves closer to the skin medially. 

Figure 71 Measurement error decreases as the 

flag table moves farther from the skin laterally. 

If we try to extend the hinge axis-locating stylus from 

the flag to the skin to mark an axis as we do in the Axi-Path 

system, the new hinge point on the skin will not correspond 

to the true hinge point. As a result, the precision mounting 

will be inaccurate. In the Axiograph III system, the measurement 

error decreases as the flag table gets farther away from 

the skin and the constructed hinge axis gets closer to the 

THA (Figure 72). 

Now let us consider two situations that we may encounter 

in clinical practice. In the first situation, the side arm of 

the upper frame contacts the skin of supraauricular area 

(Figure 73). The side arm is 6 mm wide and the flag table is 

4.5 mm thick. 

In the second situation, there may be some distance between 

the condyle and the recording flag, depending on the 

configuration of the patient’s head. For the purposes of illustration, 

we will assume that the side arm is 3 mm away from

Figure 72 

Figure 73 Supposition: The side arm contacts the skin. 

Figure 74 Supposition: The side arm is separated 

3 mm from the skin. The hinge point is measured 

at level of entrance of the clamp hole. 

the skin. In fact, this does not actually happen in clinical 

practice, because we always push the side arm onto the skin 

to fasten the upper frame to the head. If, however, we assume 

3 mm of separation, this means that the flag table will be 6.5 

mm away from the skin, and the hinge point locator clamp 

will be attached to the flag table (Figure 74). 

In this example (Figure 74) the thickness of the hinge 

axis clamp is 5.75 mm; the distance from the skin to the 

inner surface of the flag table is 6.5 mm; the distance from 

the skin to the outer surface of the flag table is 11 mm; the 

distance from the left condyle to the skin on the right side of 

is 110 + 15 mm; and the distance from the left condyle to the 

inner surface of the flag table is 110 + 15 + 6.5 mm. This is 

indicated by the yellow arrow. 

The measurement error at the position indicated by the 

arrow is calculated as follows: 

• 

Y is the measurement error on the inner surface of the 

flag table. The amount of error is 0.20 mm (Figure 75). 

Figure 75 Y is the measurement error on the inner surface 

of the flag table. The amount is 0.20 mm. 

• 

The measurement error at the inner entrance of the 

hinge axis clamp increases slightly (Figure 76). 

Figure 76 Supposition: The side arm is separated 3 mm 

from the skin. The hinge point is measured at 

level of entrance of the clamp hole. 


33

• 

• 

• 

• 

The measurement error at the inner entrance is 0.47 

mm (Figure 77). 

Figure 77 The amount of measurement error will be 0.47 mm. 

The measurement error on the skin increases even 

more (Figure 78). 

Figure 78 Supposition: The side arm is separated 3 mm 

from the skin. The hinge point is measured at 

level of entrance of the clamp hole. 

The measurement error on the skin is 0.5 mm 

(Figure 79). 

Figure 79 The amount of measurement error will be 0.5 mm. 


• 

The measurement error on the inner surface of the 

flag table is 0.20 mm and this is almost the same as 

or smaller than that of Axi-Path. 

Although the clamp hole provides a bit of leeway with 

the pin fitted, this seems to have no clinical significance. Since 

the Axiograph III system uses the hinge point on the graph, 

while the Axi-Path system uses the hinge mark on the skin, 

the two systems seem to yield almost the same accuracy in 

precision mounting (Figure 80). 

Figure 80 The measurement error on the inner surface 

of the flag table is 0.20 mm. Error is the same as, 

or less than, with Axi-Path. 

Summary and Conclusions 

The measurement errors of the hinge axis locations were 

calculated for the two recording systems, the Axi-Path of 

Panadent and the Axiograph III of SAM. The amount of 

the measurement errors were nearly the same for both systems. 

While the Axiograph III system locates the hinge axis 

using hinge points on the flag table, the Axi-Path system 

locates the hinge axis using hinge marks on the skin. Although 

the distance between the flag table and the skin is 

greater in the Axiograph, we found no significant difference 

in accuracy between the two systems, as explained 

previously. (Figure 83)

Figure 83 The distance between the flag table and the skin is longer in Axiograph III than in Axi-Path. 

But since Axiograph III uses hinge points on graph paper to locate the hinge axis, it is equally accurate. 

Since the Axiograph III system does not mark hinge 

points on the skin, it may be necessary to relocate the axes 

for each mounting. Mechanical stability of the recording device 

is very important for precision. The device must remain 

firmly seated on the head. In this respect, the Axiograph III 

seems to be superior to the Axi-Path (Figure 85). ■ 

Figure 85 Mechanical stability of the recording device is very important for precision. 

In this respect Axiograph III seems to be superior to Axi-Path. 

Further Reading 

Baldauf A, Mack H, Wirth C G. Bestommung der Scharnierachse mittels 

des äußeren Gehörgangs. IOK, 28. JAHRG. 1996. 

Broderson S P. Anterior guidance: The key to successful occlusal treatment. 

J Prosthet Dent. 1978;39:396–400. 

Cho Y, Hobo S, Takahashi H.Occlusion. Seoul: Kunja; 1996. 

Dawson P E. Evaluation, Diagnosis, and Treatment of Occlusal Problems. 

2nd ed. St. Louis, Mo: Mosby; 1989. 

Glossary of Dental Prosthodontics. Korea: Korean Association of 

Prosthodontics; 2006. 

Hobo S. Twin-tables technique for occlusal rehabilitation. Pt. 1: 

Mechanism of anterior guidance. J Prosthet Dent. 1991;66:299–303. 

Hobo S. Twin-tables technique for occlusal rehabilitation. Pt. 2: Clinical 

procedures. J Prosthet Dent. 1991;66:471–477. 

Lee R L. Panadent instruction manual for advanced articulator system. 

Panadent Corporation, CA, USA, 1988. 

Lundeen H C, Gibbs C H. The Function of Teeth. L and G; 2005. 

Nagy W W, Smithy T J, Wirth C G. Accuracy of a predetermined transverse 

horizontal mandibular axis point. J Prosthet Dent. 2002;87:387– 

394. 

Okeson J P. Fundamentals of Occlusion and Temporomandibular 

Disorders. St. Louis, Mo: Mosby; 1985. 

continued on next page... 


35

Ramfjord S, Ash M M. Occlusion. 3rd ed. Philadelphia: WB Saunders; 

1983. 

Simpson J W, Hesby R A, Pfeifer D L, Pelleu G B Jr. Arbitrary mandibular 

hinge axis locations. J Prosthet Dent. 1984;51:819–822. 

Takahashi I. Surgical-orthodontic treatment of a patient with temporomandibular 

disorder stabilized with a gnathologic splint. Am J Orthod 

Dentofacial Orthop. 2008;133: 909–919. 

Theusner J, Plesh O, Curtis D A, Hutton J E. Axiographic tracings of 

temporomandibular joint movements. J Prosthet Dent. 1993;69:209– 

215. 

Wirth C G. 20 Jahre Axiographie. IOK, 28. JAHRG. 1996. 

36 

Choi | Hinge Axis: The Need for Accuracy in Precision Mounting Part 2

Condylar Resorption, Matrix Metalloproteinases, 

and Tetracyclines 

Michael J. Gunson, DDS, MD ■ G. William Arnett, DDS, FACD 

mic h a e L J. Gu n S o n , ddS, md 

gunson@arnettgunson.com 

■ Graduated from UCLA School of 

Dentistry, 1997 

■ Graduated from UCLA School of 

Medicine 2000 

■ Specialty Certificate in Oral and 

Maxillofacial Surgery UCLA, 2003 

G. Wi L L i a m aR n e T T , ddS, Facd 

■ Graduated from USC School of 

Dentistry, 1972 

■ Specialty Certificate in Oral and 

Maxillofacial Surgery UCLA, 1975 

Introduction 

Orthodontists and maxillofacial surgeons are well acquainted 

with the effects of condylar resorption (Figure 1). 

Figure 1 Tomograms reconstructed from cone-beam CT scan. 

They show severe condylar resorption in a 19-year-old female 

over a 2-year period. Note the progressive osseous destruction. 

The clinical outcomes of condylar resorption have been described 

at length in the literature. 1-6 The causes, however, 

have been elusive, hence the common name idiopathic condylar 

resorption. Over the last several years, the pathophysiology 

of articular bone erosion secondary to inflammation 

Summary 

Mandibular condylar resorption occurs as a result of inflammation and hormone 

imbalance. The cause of the bone loss at the cellular level is secondary 

to the production of matrix metalloproteinases (MMPs). MMPs have been 

shown to be present in diseased temporomandibular joints (TMJs). There is 

evidence that tetracyclines help control bone erosions in arthritic joints by 

inactivating MMPs. This article reviews the pertinent literature in support of 

using tetracyclines to prevent mandibular condylar resorption. 

has been well studied. A number of cytokines and proteases 

are found in joints that show osseous erosions that are not 

present in healthy joints, namely TNF-α, IL-1β, IL-6, and 

RANKL and matrix metalloproteinases. 

Matrix Metalloproteinases 

MMPs are of interest because they are directly responsible 

for the enzymatic destruction of extracellular matrix in normal 

conditions (angiogenesis, morphogenesis, tissue repair) 

and in pathological conditions (arthritis, metastasis, cirrhosis, 

endometriosis). MMPs are endopeptidases that are made 

in the nucleus as inactive enzymes, or zymogens. The zymogens 

travel to the cell membrane, where they are incorporated. 

The zymogen is then cleaved into the extracellular matrix 

as the active enzyme, where it makes cuts into the protein 

chains (collagen types I through IV, gelatin, etc). These cuts 

cause the proteins to denature, which results in the destruction 

of the matrix. The action of the MMP requires the mineral 

zinc—which is an important part of the MMP’s protein 

structure; hence the name metalloproteinase (Figure 2). 


37

Figure 2 The zymogen pro-MMP is transcribed in the nucleus 

and then attached to the cell membrane. It is activated when 

it is cleaved from the membrane. The zinc (Zn) portion binds 

to protein and the enzyme cleaves the protein, destroying the 

extracellular matrix. 

In joints, MMPs are produced by monocytes, mac- 

rophages, polymorphonuclear neutrophils, synoviocytes, osteoblasts, 

and osteoclasts. MMPs are generally classified by 

the kind of matrix they degrade; thus collagenase, gelatinase 

and stromelysin (Figure 3). 

Figure 3 A list of the 28 known MMPs. They are generally 

named after the extracellular protein that they degrade. 

The extracellular activity of MMPs is regulated in two 

ways, by transcription and by extracellular inhibition. The 

transcription of MMPs in the nucleus is controlled by multiple 

pathways. MMP transcription is activated by sheer stress 

to the cell, by free radicals, and by the cytokines TNF-α, IL- 

1β, Il-6 and RANKL (Figure 4a). Transcription is suppressed 

by the cytokine osteoprotegerin and by the the hormones 

vitamin D and estradiol (Figure 4b). After transcription, the 

pro-MMP is then sent to the cell membrane, where it is incor- 

38 Gunson, Arnett | Condylar Resorption, Matrix Metalloproteinases, and Tetracyclines 

porated. Activation of the MMP occurs when the active side 

of the MMP is cleaved from the cell and liberated into the extracellular 

matrix. Extracellular inhibition comes from proteins 

called tissue inhibitors of metalloproteinases (TIMPs). 

TIMPs bind to active matrix metalloproteinases and inhibit 

their activity (Figure 4c). The ratio of MMP:TIMP activity 

influences the amount of matrix degradation. 7-10 

Figure 4-a MMP transcription is activated in the cell nucleus by 

cytokines (TNF-α, IL-1β, Il-6, and RANKL); by metabolic 

by-products (free radicals); and by direct sheer stress 

to the cell membrane. 

Figure 4-b MMP transcription is inhibited by hormones such 

as vitamin D and estradiol, as well as the bone-protective 

cytokine osteoprotegerin.

Figure 4-c The extracellular activity of MMPs is controlled by the 

presence of inhibitory proteins called tissue inhibitors of 

metalloproteinases, or TIMPs. TIMPs bind directly to the 

MMPs, causing conformational changes that prevent the 

destruction of matrix proteins. 

MMPs and Arthritis 

The hallmark sign of arthritis is articular bone loss. In the 

past, clinicians have differentiated between inflammatory arthritis 

and osteoarthritis (OA). Recently, however, the cellular 

processes that result in bone and cartilage loss in both forms 

of arthritis have been shown to be quite similar. 11 While inflammatory 

arthritis is promoted by a systemic problem, the 

result is an inflammatory cytokine cascade, which ultimately 

results in osteoclastic activity and bone loss at the articular 

surface. OA is not a systemic problem but a local one, secondary 

to oxidation reactions, free radical production, or sheer 

stress—all three of which result from overuse. 12, 13 Despite 

the localized nature of OA, the cascade of cellular events that 

cause articular surface loss is the same as the systemically induced 

cascade. An increase in TNF-α and IL-1β increases the 

number of osteoclasts and their activity. TNF-α, IL-1β, IL- 

6, and RANKL all cause increased expression of the MMP 

genes. The end result is destruction of cartilage, bone, and 

connective tissue in both arthritis models. 14-18 

MMPs also respond to systemic hormones such as estrogen, 

vitamin D, and parathyroid hormones. We found an association 

between low estrogen levels and low vitamin D levels 

in patients with severe condylar resorption. 3 All of these 

hormones and cytokines are intimately involved in osteoclast 

differentiation and activation. This makes sense: MMPs are 

osteoclast produced and are responsible for bone and cartilage 

destruction. 

MMPs and the TMJ 

There is substantial evidence indicating that MMPs play an 

important role in bone and cartilage degradation associated 

with degenerative temporomandibular joint (TMJ) arthriti- 

des. This evidence supports the presence of 6 of the known 

28 matrix metalloproteinases (MMP-1, MMP-2, MMP-3, 

MMP-8, MMP-9, and MMP-13) in fluid or tissue samples 

obtained from diseased human TMJs. 13, 16, 17, 19-34 Some cases 

of degenerative joint disease also result from an imbalance 

between the activities of MMPs and TIMPs, favoring unreg- 

35, 36 

ulated degradation of tissue by MMPs. 

Tetracyclines 

Because MMPs are found to be elevated in patients with 

TMJ arthritis and are so destructive to articular tissues, finding 

a way to reduce their activity or their production would 

be helpful in treating patients with arthritis and condylar 

resorption. 

From 1972-1982, at the School of Dental Medicine in 

Stony Brook New York, Ramurmathy and Golub discovered 

that tetracyclines have anti-collagenolytic properties. 

In 1998, Golub and colleagues showed that tetracyclines 

inhibit bone resorption in two ways—by controlling the expression 

and activity of MMPs and by regulating osteoclasts 

and their activity. 37 

Controlling MMPs With Tetracyclines 

Tetracyclines inhibit MMPs by chelating zinc and by regulating 

MMP gene expression. As noted above, MMPs need 

zinc to actively cleave collagen proteins. Tetracyclines bind 

divalent ions, such as zinc. By reducing the amount of free 

zinc in tissues, tetracyclines reduce the number of MMPs 

available. 38 In addition, tetracyclines bind to the MMP itself, 

which causes a conformational change in the enzyme, inactivating 

it (Figure 5). 39 Tetracyclines have also been shown to 

decrease the transcription of MMPs by blocking both pro- 

40, 41 

tein kinase C and calmodulin pathways. 

Figure 5 Tetracycline binds directly to the zinc of the MMP. 

This deactivates the enzyme and protects the matrix 

from degradation. Tetracycline also controls osteoclastic 

activity and MMP transcription. 


39

Regulating Osteoclasts With Tetracyclines 

Osteoclasts are responsible for the breakdown of bone and 

cartilage. Their activity is tightly controlled by cytokines 

such as IL-6, TNF-α, nitric oxide, and IL-1β. Tetracyclines 

have been shown to prevent the liberation of these cytokines, 

diminishing the activity of osteoclasts. 42-46 Tetracyclines also 

prevent the differentiation of osteoclast precursor cells into 

osteoclasts. 47 Finally, tetracyclines promote the programmed 

cell death (apoptosis) of osteoclasts. 48, 49 All these actions result 

in a decrease of bone and cartilage loss secondary to 

osteoclast activity when tetracyclines are present. 

Tetracyclines and Arthritis 

In short, the literature shows that tetracyclines exert control 

over MMP transcription and activity and regulate osteoclast 

activity as well. The clinical evidence supporting the use of 

tetracyclines to protect articular bone and cartilage from arthritic 

inflammation is encouraging. 

In the animal model of arthritis, tetracyclines have been 

shown to inhibit MMPs and to prevent the progression of 

osseous disease. 50-52 Yu et al52 induced knee arthritis in dogs 

by severing the anterior cruciate ligament. Half the dogs 

were pretreated with doxycycline. Doxycycline prevented 

the full-thickness cartilage ulcerations that were seen in the 

untreated group. 

In human studies, tetracyclines have been successfully 

used to diminish bone erosions in patients with inflammatory 

arthritis. One meta-analysis of 10 clinical trials that used 

tetracycline for rheumatoid arthritis (RA) showed significant 

improvement in disease activity with no side effects. 53 In a 

single-blinded controlled study, doxycycline was shown to 

be as effective as methotrexate in treating inflammatory ar- 

thritis. 54 

Israel et al reported that doxycycline administered at a 

dose of 50 mg twice daily for 3 months significantly suppressed 

MMP activity in three patients diagnosed with advanced 

osteoarthritis of the TMJ. Two of the three patients 

reported marked improvement in symptoms, including improved 

mandibular range of motion. One patient did not 

experience symptomatic relief despite a marked reduction in 

MMP activity. 55 While symptomatic relief would be important, 

it must be noted that inhibition of MMPs has a direct 

effect on bony resorption, which is often unrelated to TMJ 

symptoms. Clinicians need to keep this in mind when reviewing 

the literature. 

Dosing 

At present, there are no definitive studies demonstrating the 

efficacy of tetracycline therapy for degenerative TMJ arthritides. 

However, based on the available information, tet- 


racyclines may be considered for the treatment of rapidly 

progressive condylar resorption, and in patients with degenerative 

TMJ disease. They may also be used in patients at increased 

risk for resorption. This includes patients with bruxism, 

inflammatory arthritis, or a past history of resorption 

who are undergoing occlusal treatment. Of all the available 

tetracyclines, Golub et al found that doxycycline was the 

most effective at suppressing MMP activity. 56 Appropriate 

studies to determine effective dose schedules have not been 

conducted to date. However, based on the limited clinical 

data, it is reasonable to consider doxycycline at a dose of 50 

mg twice daily. 

Side Effects 

The adverse effects of tetracyclines are well known. They 

include allergic reactions; gastrointestinal symptoms (ulcers, 

nausea, vomiting, diarrhea, Candida superinfection); photosensitivity; 

vestibular toxicity with vertigo and tinnitus; decreased 

bone growth in children; and discoloration of teeth 

if administered during tooth development. Tetracyclines may 

also reduce the effectiveness of oral contraceptives, potentiate 

lithium toxicity, increase digoxin availability and toxicity, 

and decrease prothrombin activity. 57 

If tetracycline therapy is initiated, the patient should be 

advised of the potential for reduced efficacy of oral contraception. 

In addition, the patient should be cautioned against 

sun exposure, and should be monitored for other side effects. 

If surgery is contemplated, the patient’s coagulation status 

should be evaluated. 

There is some question as to whether bacterial resistance 

may develop with the chronic use of antibiotics. Studies 

show that long-term low-dose doxycycline (20 mg twice 

daily) does not lead to a significant increase in bacterial resis- 

58, 59 

tance or to a change in fecal or vaginal flora. 

Other Medications to Control MMPs 

Tetracyclines are not the only medications that can prevent 

MMP-induced bone erosions. There are promising studies 

that show the benefits of TNF-α inhibitors; osteoprotegerin 

analogues; HMG-CoA reductase inhibitors (eg, simvastatin); 

and hormone replacement therapies, including vitamin 

D and estradiol. 60-63 These medications, along with doxycycline, 

show great promise in controlling articular bone loss 

in the face of inflammation. 

Conclusion 

When patients present with condylar resorption, clinicians 

have long been resigned to two choices: watch and wait or 

surgical resection with the resulting disability and deformity. 

Doxycycline is just one pharmacological intervention that

shows promise in curbing the bone loss associated with arthritis 

and condylar resorption (Figures 6-a, b, c, d, e). ■ 

Figure 6-a, b, c, d, e This is a 31-year-old patient with condylar 

resorption secondary to rheumatoid arthritis. She was treated 

with orthognathic surgery to correct her malocclusion. The 

effects of MMPs were controlled pre- and postoperatively by 

prescribing the following medications: doxycycline, simvastatin, 

Enbrel, Feldene, vitamin D, and omega-3 fatty acids. She is 10 

months postsurgery with minimal osseous change to her condyles 

and a stable class I occlusion with good overbite and overjet. 


41

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43

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44 Gunson, Arnett | Condylar Resorption, Matrix Metalloproteinases, and Tetracyclines

Comparison of Maxillary Cast Positions Mounted from a True Hinge 

Kinematic Face-Bow vs. an Arbitrary Face-Bow in Three Planes of Space 

Dori Freeland, DDS, MS ■ Theodore Freeland, DDS, MS 

■ Richard Kulbersh, DMD, MS, PLC ■ Richard Kaczynski, BS, MS, PhD 

doR i FR e e L a n d, ddS, mS 

tdfortho@freelandorthodontics.com 

■ Private Practice, Lake Orion, MI 

The o d o R e FR e e L a n d, ddS, mS 

■ Adjunct Professor, Orthodontic 

Dept., School of Dentistry, 

University of Detroit Mercy 

■ Director Roth/Williams USA 

■ Private Practice, Gaylord, MI 

Ric h a R d Ku L b e R S h, dmd, mS, PLc 

■ Program Director, Orthodontic 

Dept., School of Dentistry, 

University of Detroit Mercy 

Ric h a R d Ka c z y n S K i , bS, mS, Phd 

■ Statistician, Dept. of Psychiatry, 

Yale University School of Medicine 

Introduction 

The quest to understand the multifaceted movements of 

the mandible and its relationship to the rest of the cranial 

complex began in the early 1800s. 1 Gray’s Anatomy was 

one of the first sources to publish the fact that the mandible 

moves on a hinge as well as by forward and lateral movements 

from the condyles in the glenoid fossae. 1 Thus, the 

temporomandibular joint (TMJ) became known as a ginglymo-arthrodial 

joint and was seen as one of the most complex 

joints in the human body. Although the TMJ is considered 

a compound joint, it consists of only two actual bones. An 

articular disc interposed between the condyles and the mandibular 

fossa of the temporal bone keeps the two bones from 

direct articulation. The disc serves as a nonossified bone; it 

serves as the third bone of the compound joint and allows 

complex movements to occur. 2 

When occlusal function is ideal, the condyles are positioned 

in the glenoid fossae and the mandible should be 

able to move by joint-dictated patterns without any interfer- 

Summary 

There are many methods of performing a face-bow transfer, but only two 

current methods of replicating the position of the maxilla in three planes of 

space: with a true hinge face-bow or with an arbitrary earpiece face-bow. The 

purpose of this study was to determine if a clinically significant difference in 

three planes of space occurs in the mounting of the maxillary cast when the 

mounting is done with an arbitrary earpiece face-bow versus a true hinge 

face-bow. 

The sample consisted of 51 subjects with complete permanent dentitions 

through the second molars, including class I, class II, and class III subjects. 

Two maxillary impressions were taken on each subject. One maxillary cast 

was mounted using an arbitrary earpiece face-bow and the other using a true 

hinge face-bow. Each cast was measured and compared in three planes of 

space on an adjustable occlusal table containing graph paper. The positions 

of the maxillary right central and right and left first molars were recorded for 

the true hinge mounting in red on the graph paper and the arbitrary earpiece 

face-bow measurements were recorded in blue. The vertical, anteroposterior 

(A-P), and transverse differences between the two mountings were recorded, 

and a paired t-test was used to analyze the data. The two face-bow techniques 

were statistically significantly different in all three planes of space (p ≤ .001). 

ence from the teeth. 3 According to Okeson, this position is 

achieved when the muscles of mastication and the ligaments 

combine to seat the condyle into the glenoid fossa. 2 Stability 

of the joint is maintained by constant muscle activity, even 

in resting states, which allows the articular surfaces to come 

into contact, although a true structural attachment or union 

is not present in the TMJ. 2 The muscles play an active role in 

the opening and closing of the mandible, while the ligaments 

act as passive restraining devices to limit joint movements. 

Specifically, the temporomandibular ligament plays a role 

in limiting the extent of mouth opening. During the initial 

phase of opening, the condyle rotates around a fixed point 

for about 20 mm, until the temporomandibular ligament 

becomes strained and the condyle is forced into a forward 

movement down the articular eminence. 2 Posselt defined 

this opening as the mandibular terminal hinge opening and 

closing. 4 The Glossary of Prosthodontic Terms similarly describes 

this movement as “an imaginary line around which 

the mandible may rotate through the sagittal plane” and 


45

terms the movement the transverse horizontal axis. 5 

Study of mandibular movements raised questions among 

the dental profession as to whether a hinge axis actually exists, 

and if so, whether it is one axis or more than one. The 

dental profession also debated how accurately the hinge axis 

can be located, if in fact one exists; the clinical usefulness of 

locating it; and whether an arbitrary point on the face can 

satisfactorily be substituted for a specific point as a location 

for the hinge axis. 6 No other topic inspires more controversy 

in oral physiology than the role of the jaw joints in dental 

articulation. 

Campion, working in 1902, made the first graphic 

record of the mandibular movements in a patient. He concluded 

that both a rotation of the bone on an axis and a 

forward-downward movement of the condyles occurred. 

Campion designed an adjustable face-bow fixed to the mandibular 

teeth with modeling plaster to graphically record the 

various positions of the condyles on the face with a succession 

of dots. He concluded that “the only part of the opening 

movement which an articulator reproduction is concerned 

with is the initial stage, which is seen in the tracings to be a 

7, 8 

simple rotation about an axis passing through the condyles.” 

Bennett also recognized that the mandible was capable of 

two independent movements, but he felt that no single fixed 

center of rotation for the mandible existed. 8 He judged that 

the initial center of rotation of the mandible was located behind 

and below the condyle. 8 

During this same period, Stallard introduced the term— 

and the concept of—gnathology—the study of the harmonious, 

interrelated functioning of the jaws and teeth. 1,7,9 In 

1924, McCollum developed the first method of locating the 

hinge axis with an instrument called the gnathoscope, and 

its later model, the gnathograph. 1,7 McCollum demonstrated 

that no external anatomical landmarks would indicate the 

position of the opening axis, nor could this be done by palpating 

the joint or by measuring a distance in any direction. 1,7 

McCollum explained that the hinge axis must be determined 

instrumentally, and that the movement of this axis is a component 

of every masticatory movement of the mandible. 1,7 

After McCollum’s death, Stuart continued to study mandibular 

movement and developed his own gnathological system, 

including a fully adjustable articulator and pantograph. 1,7 

Gnathologically oriented studies produced and still produce 

conflicting conclusions that divide the dental community. 

One group believes that there is a definite transverse 

hinge axis, and that it is necessary to find its point of rotation. 

Another group believes that methods of locating an 

arbitrary hinge point are just as reliable, and more operator 

friendly. Still others believe that it is not necessary to locate 

the transverse axis at all. 

46 Freeland et al | Comparison of Maxillary Cast Positions 

Trapozzano and Lazzari found that 57.2% of the subjects 

in their study had more than one condylar hinge axis 

point located on either one or both sides of the mandible. 

Therefore, the attempt to locate the hinge axis, was seriously 

questioned because multiple axis points may exist. 10,11 Other 

studies have demonstrated that the center of rotation is movable 

during every phase of jaw opening and closing; therefore 

these studies also refute the hinge axis theory. 12,13 Still 

other studies have questioned the use of a hinge axis, due 

to the complexity of its location, and the technical operator 

error that is inherent in the procedure. 14,15 Many investigators 

believe that it may be impractical to construct clutches, 

locate the hinge axis, make multiple interocclusal records, 

and use a fully adjustable articulator on every patient. 16 Still 

the theory that the hinge axis is a reliable reference—one in 

which the position of the maxillary cast on an articulator can 

be reproduced—is a very strong one. 4 

Many studies have demonstrated that the terminal hinge 

movements of the mandible pass through both condyles. 

These studies support the theory that there is only one hinge 

axis . 4,17-19 Beard and Clayton reached this conclusion by using 

an apparatus that records arcs on paper; they argued that 

the terminal hinge axis can be accurately located by finding 

the one and only stylus position where no arcing occurs. 19 

There are many methods of locating the arbitrary hinge 

axis for transfer to an articulator. Following are some examples 

of these methods. 

1. The Gysi point is located 13 mm in front of the 

most upper part of the external auditory meatus on 

a line passing to the ectocanthion. 

2. The Lauritzen-Bodner axis is located 12 mm anterior 

to and 2 mm below the porion. 

3. Abdal-Hadi axis is located using a linear regression 

formula to predict the anteroposterior (A-P) site of 

the hinge point, according to the width profile axis 

theory of the face. 

4. The arbitrary hinge axis is located using the earpiece 

face-bow. In this method, the ear rods of a 

fixed face-bow are inserted into the external auditory 

meati. 

5. The arbitrary hinge axis is located by external palpation 

of the condylar anatomy. 20,21 

Studies have shown that when an arbitrary earpiece 

face-bow is used to reproduce the condylar positions, the 

results are fairly reliable. 22-27 Clinically, it has become acceptable 

that as long as the arbitrary point is within 5 mm of the 

true hinge axis, the arbitrary earpiece face-bow is accurate 

enough to study the patient’s occlusion. 22-27 Nagy et al conducted 

another study comparing the location of an anatomically 

predetermined hinge axis point with marked hinge axis

points. They found that the mean distance between any two 

points was 1.1 mm. More than 96% of predetermined points 

were within 2 mm of the true hinge axis. 23 Schallhorn also 

found that approximately 98% of all true anatomical hinge 

axis points were within a 5-mm radius. 26 

In comparison, studies that compared maxillary cast positions 

mounted with four different face-bows showed wide 

variation in the mounted maxillary cast positions. All arbitrary 

hinge axis points deviated from the true hinge baseline 

point by anywhere from 1.5 mm to 4 mm. Therefore, the 

authors of these studies concluded that it was not possible 

to establish the clinical superiority of one arbitrary face-bow 

over another. 28,29 

Lauritzen and Bodner located 100 true hinge points on 

50 subjects. They found that 67% of the axis points were 

5 mm to 13 mm away from the arbitrarily marked hinge 

points. This discrepancy may introduce gross errors in the 

mounting of the casts on an articulator, resulting in large 

occlusal errors. 30 Palik et al got similar results. They found 

that only 50% of the arbitrary hinge axes located with the 

arbitrary earpiece face-bow were within a 5-mm radius of 

the terminal hinge axis. This indicated that the arbitrary 

earpiece face-bow hinge axis location does not represent the 

total population. 31 Schulte et al concluded from their study 

that errors in locating the arbitrary hinge axis will produce 

a three-dimensional occlusal error. 32 This study and others 

have recommended that if a thick vertical dimension of wax 

was used for an interocclusal record, or if the vertical dimension 

will be changed with treatment, a true hinge axis should 

be located on the patient. 32,33 Due to anatomical variations, 

the arbitrary earpiece face-bow may introduce significant errors 

in an A-P or vertical dimension, resulting in mandibular 

displacement. 34,35 The only way to be relatively certain that 

errors due to malpositioning of maxillary casts on an articulator 

have been avoided is to locate the true hinge axis. 30,36-40 

Studies indicate that coincidence between the two hinge 

axis points does not usually occur. 41 This results in a discrepancy 

between the arbitrary hinge axis and the true hinge axis 

points. This discrepancy will cause changes in the mounted 

position of the maxillary cast, which in turn can produce a 

positional change of all teeth in the three planes of space. 41 

Zuckerman mathematically demonstrated that discrepancies 

between the true hinge axis and the arbitrary hinge axis points 

can produce changes in the A-P direction of the occlusion. He 

verified in his analog tracing that the arc of the incisal edge 

does not change in the A-P direction in centric occlusion, as 

long as the mandible is also coincident in centric relation. 

However, when an error in the arbitrary hinge axis occurs 

and it is anterior to the true hinge, the incisor arc of closure 

is anterior to the actual arc of closure. 41 Errors in the verti- 

cal position of the arbitrary hinge axis (AHA) produce the 

largest A-P discrepancies upon mandibular closing. 41 Other 

authors have graphically illustrated how errors in true hinge 

axis location can produce occlusal aberrations. 33,35,36,42 These 

authors also showed that the greatest errors occurred when 

the hinge axis was incorrectly located in a vertical direction 

perpendicular to the correct hinge axis closure. An arbitrary 

hinge axis positioned superior to the true hinge axis also 

produced premature contacts on the anterior teeth. In addition, 

if the arbitrary hinge axis was placed inferior to the true 

hinge axis, premature posterior contacts occured. 33,35,36,42 

Brotman’s geometric representation related changes in 

the hinge axis point locations between the true hinge axis 

and the arbitrary axis to differences produced at the occlusal 

level in mounted casts. 43 Brotman concluded that “if the 

hinge axis has been improperly located by as much as 3 mm, 

the error at the occluding position of the casts (anteroposteriorly) 

will be about .09 mm or less than 1/250 inch.” 43 

Gordon et al looked at the location of the terminal hinge 

axis and its effect on the second molar cusp position on the 

position of the second molar cusp. 6 Their results showed that 

incorrect anterior location of the hinge axis produced the effect 

of having moved the mandibular arch backward. Incorrect 

posterior location of the hinge axis produced the effect 

of having moved the mandibular arch forward. Incorrect inferior 

location of the hinge axis caused slight retrusion of the 

mandibular cast with premature posterior contacts. Incorrect 

superior location of the hinge axis caused protrusion of the 

mandibular cast with premature anterior contacts. 6 

Since studies vary in reporting the percentage of placement 

of the arbitrary hinge axis less than 5 mm from the true 

hinge axis, it can be assumed that larger errors in occlusion 

may occur. It has been found that an occlusal discrepancy of 

0.01 inch can cause pulpitis or periodontal disease, though 

the patient may not be able to detect so small a discrepancy. 44 

To limit occlusal errors in mountings, it is necessary to locate 

the hinge axis to within 1 mm, and the kinematic true hinge 

can be done to this degree of accuracy. 44 Therefore, the importance 

of the true hinge axis is substantial when changing 

the vertical dimension upon mandibular closure. 38 

Orthodontics deals specifically with the movement of 

all teeth and their occlusal fit. Therefore, it calls for extreme 

accuracy during diagnosis, treatment planning, and rendering 

treatment. 9 Clinically finding the true hinge axis may be 

the only way to ensure a reproducible and accurate starting 

point—one from which optimum esthetic and functional results 

can be obtained. 6,38,45 The purpose of this study was to 

compare the maxillary cast mountings of 51 patients in three 

planes of space when mounted using a true hinge axis facebow 

versus an arbitrary earpiece face-bow. 


47

Materials and Methods 

The records of 51 patients—34 females and 17 males—treated 

in a gnathologically oriented practice constituted the sample. 

Subjects ranged in age from 13 to 57 years, and all had 

unremarkable medical histories with no contraindications to 

orthodontic treatment. All upper and lower permanent teeth, 

except third molars, were present on all subjects. TMJ exams 

were conducted by a single operator before orthodontic records 

were conducted. Evaluation included subjective symptomatology, 

as well as clinical examination. Subjects who 

presented with TMJ symptoms were placed on a gnathological 

maxillary splint for a minimum of 3 months, or until 

subjects were symptom free. Twenty of the 51 subjects had 

records taken after splint therapy. The remaining 31 subjects, 

all in active orthodontic treatment and with asymptomatic 

TMJ, had records taken one appointment prior to deband. 

All subjects had two maxillary alginate impressions taken 

using Jeltrate alginate (Dentsply, Milford, Delaware). The 

impressions were taken using sterilized metal rim lock trays 

(Dentsply, Milford, Delaware). All impressions were disinfected 

using Sterall Plus Spray (Colgate-Palmolive Company, 

Canton, Massachusetts), and were rinsed with water and air 

dried before being poured up. 

All impressions were wrapped in moistened paper towels 

and placed in plastic bags for approximately 20 minutes 

prior to being poured up with Velmix (KerrLab, Orange, 

California). Each model was poured up utilizing a waterpowder 

ratio consistent with the manufacturer’s instructions 

for Velmix. The Velmix was vacuum mixed to remove any 

entrapped air. The models were trimmed, and all bubbles 

were removed from the occlusal surfaces. 

Arbitrary earpiece face-bow transfers using the external 

auditory meati were taken on each subject. (Panadent, Grand 

Terrace, California) (Figure 1). 


Figure 1-a, b Estimated facebow. 

Figure 1-b 

A true hinge face-bow was then taken on each subject, 

using the true hinge axis instrument (Panadent, Grand Ter- 

race, California) (Figure 2). A single operator completed 

both face-bow records within 20 minutes of each procedure. 

Intraoperator reliability tests for each of the two transfer 

techniques were calculated.

Figure 2-a, b True-hinge facebow. 

Figure 2-b. 

One maxillary cast was mounted using the true hinge 

kinematic face-bow transfer on a single Panadent articulator 

(Panadent, Grand Terrace, California), with Snow White 

Plaster #2 (Kerrlab, Orange, California) mixed according to 

the manufacturer’s instructions. The second maxillary cast 

was mounted with the arbitrary face bow on a single Panadent 

articulator (Panadent, Grand Terrace, California), using 

the same mounting plaster as was used for the first cast. 

The true hinge maxillary cast was placed on a single 

Panadent articulator, and an adjustable occlusal table (Panadent, 

Grand Terrace, California), with graph paper adhered 

to the surface, was attached to the articulator in place of the 

mandibular cast. With the occlusal pin at zero, the occlusal 

plane relater was stabilized by allowing contact at the maximum 

number of maxillary cast teeth (Figure 3). 

Figure 3 Maxillary cast mounted with 

occlusal relater and pin at zero. 

A 1-mm step ruler (Panadent, Grand Terrace, California) 

was used to measure the vertical distance of the mesiobuccal 

cusp tip of the right and left first permanent molar and the 

upper right central incisor (Figure 4). 

Figure 4-a Vertical measurements with 1-mm 

incremental step ruler: Measurement of anterior tooth 

vertical discrepancy. 

Figure 4-b Vertical measurements with 1-mm 

incremental step ruler: Measurement of posterior tooth 

vertical discrepancy. 


49

A straight wire with a 90-degree bend at the tip was 

held with the handle parallel to the occlusal plane relater 

(Figure 5). 

Figure 5 Straight-lined measurement instruments. 

The tip was placed perpendicular to the tooth and held 

touching the height of contour of the upper first permanent molars 

and the upper right permanent central incisor (Figure 6). 

Figure 6 Articulating paper used with straight-lined 

measurement instrument for tooth markings. 

It was then used to mark the position of the mesiobuccal 

cusp of the upper molars and the entire incisal-edge position 

of the upper central incisor. Red articulating paper for the 

maxillary cast mounted with the true hinge axis face-bow 

mounted maxillary cast was then placed beneath each tooth 

(Figure 7). 

Figure 7 Tooth markings on graph paper. 


This allowed the instrument to register the position of 

each tooth on the graph paper (Figure 8). 

Figure 8 Comparing arbitrary hinge axis points vs. 

true hinge axis point: 

1= Lower incisor will arc closed posterior to actual arc of closure 

if AHA is inferior to TH. 

2= Lower incisor will arc closed anterior to actual arc of closure 

if AHA is superior to TH. 

3= Lower incisor will arc closed slightly posterior to actual arc of 

closure if AHA is anterior to TH. 

4= Lower incisor will arc closed slightly anterior to actual arc of 

closure if AHA is posterior to TH. 

The occlusal plane relater was left in place, and the same 

measuring procedure was then conducted on the maxillary 

cast mounted with the estimated face-bow, utilizing blue articulating 

paper. A new sheet of graph paper was adhered to 

the occlusal plane relater each time a new set of casts was 

measured. 

To measure the differences between the red and blue 

markings, a Boley gauge was used. Five total measurement 

comparisons were done. The first measurement assessed the 

change in vertical dimension between the casts at the mesiobuccal 

cusp tip of the maxillary right permanent first 

molar. The second measurement assessed the vertical discrepancy 

of the upper left first permanent molar. The third 

measurement assessed the vertical discrepancy between the 

upper right permanent central incisors. The fourth measurement 

compared the difference in an A-P direction between 

the mesiobuccal cusp tips of the upper right and left first 

permanent molars. The fifth measurement assessed the transverse 

discrepancy between the mesiobuccal cusp tips of the 

upper molars. All measurements were conducted by a single 

operator. Intraoperator reliability testing was used to validate 

this measurement technique. 

Results 

A two-tailed matched-pairs t-test was used to evaluate for 

significant difference in occlusal measurements in three 

planes of space between maxillary casts mounted with a true 

hinge face-bow and mounted with an estimated face-bow. 

For this experiment, an α level of 0.05 was chosen. Given 

the number of measurements being evaluated (8), we decided

to adjust for experimentwide error by reducing our desired 

significance level to 0.001. 

Measurements 

Table 1 Mean values of the two face-bow techniques. 

Table 1 shows the means and standard deviations for 

the arbitrary face-bow technique and the true hinge facebow 

technique in the vertical, A-P, and transverse dimensions 

with respect to the maxillary right and left first molars and 

the maxillary right central incisor. The mean measurements 

taken on the cast mounted with a true hinge face-bow were 

significantly smaller than those measured on the arbitrary 

earpiece face-bow mountings. The standard deviations for 

the true hinge face-bow were also one-half to one-third 

smaller, indicating less variation around the sample mean. 

Results of the paired t-test are shown in Table 2. 

Table 2 Paired t-tests for differences between 

estimated and true hinge technique. 

The two face-bow techniques differed significantly in 

all three planes of space. The mean vertical discrepancy of 

the maxillary right first molar between the estimated and the 

true hinge face-bow was 2.19 +/- 2.31 (t = 6.76, df = 50, p 

< .001). The mean vertical discrepancy for the maxillary left 

first molar was 2.45 +/- 2.21 (t = 7.90, df = 50, p < .001). 

The mean vertical discrepancy for the upper right central 

was 1.90 +/- 1.75 (t = 7.76, df = 50, p < .001). 

The mean difference in the A-P dimension was 3.82 +/- 

5.51 (t = 8.163, df = 50, p < .001) for the maxillary right first 

molar and 3.10 +/- 2.63 (t = 8.28, df = 50, p < .001) for the 

maxillary left first molar. The maxillary right central incisor 

showed a mean difference of 3.05 +/- 2.62 (t = 8.25, df = 50, 

p < .001). Finally, the transverse dimension was evaluated. 

The mean difference for the maxillary right first molar was 

2.23 +/- 1.33 (t = 12.11, df = 50, p < .001). The mean differ- 

ence for the maxillary left first molar was 2.60 +/- 1.49 (t = 

11.57, df = 50, p < .001). 

The measurement differences in the vertical direction of 

the maxillary right first molar ranged from 0.0 to 3.0 mm. 

The measurement differences in the vertical direction of the 

maxillary left second molar ranged from 1.0 mm to 3.0 mm. 

The measurement differences in the vertical direction of the 

maxillary upper right central incisor ranged from 0.0 to 5.0 

mm. The differences in the A-P dimension of the upper right 

molar ranged from 0.0 to 13.1 mm; of the upper left molar 

from 0.0 to 15.0 mm; and of the upper central incisor from 

0.0 to 13.0 mm. The differences in the transverse dimension 

ranged from 0.0 to 7.0 mm for the upper right first molar 

and from 0.5 to 7.9 mm for the upper left first molar. 

Discussion 

Mounting dental casts on an articulator allows the clinician 

to simulate maxillo-mandibular position in centric relation 

and makes possible a visible simulation of mandibular border 

movements. It has been recommended that mounting 

diagnostic dental casts on an articulator should be incorporated 

into routine clinical orthodontic practices. 3,46 Recording 

the hinge axis and transferring it to an articulator is of 

considerable value in the diagnosis and treatment of occlusal 

malfunction. 42 In this diagnostic process, a face-bow transfer 

is one of the first steps in taking accurate intermaxillary 

records. Many face-bow techniques are in use today. 20,21 

However, this study conducted a comparison of only two 

face-bow techniques, an arbitrary earpiece face-bow and a 

true hinge face-bow. 

The null hypothesis for this study: “There is no difference 

in the vertical, horizontal, or transverse position of the 

maxillary cast mounted with a true hinge face-bow versus an 

arbitrary earpiece face-bow” was rejected. Paired t-tests indicated 

that the maxillary cast position using an arbitrary facebow 

transfer was significantly different in all three planes of 

space from the maxillary cast position mounted using a true 

hinge face-bow transfer. 

In previous comparison studies when the arbitrary earpiece 

face-bow is located anywhere along a 5-mm radius of 

the true hinge axis point, some authors have found that the 

mandibular arc of closure may not be very different from the 

true hinge arc of closure. 21,26,39,40,42 However, Lauritzen and 

Bodner found that in only 33% of the 50 patients they examined 

did the arbitrary hinge point fall within 5 mm of the 

true hinge point. In the other 67%, the arbitrary hinge points 

were 5 mm to 13 mm away from the true hinge points. Arbitrary 

markings of the hinge axis introduce severe errors 

in mounting casts on an articulator, which may introduce 

occlusal errors in the centric jaw relation record. 30 Ricketts 


51

found that there can be extreme variation in the soft tissue 

around the ear. 34 This variation can make it difficult to locate 

the hinge point with an arbitrary earpiece face-bow. 

The present study found larger mean values for the arbitrary 

earpiece face-bow measurements. This suggests that the true 

hinge face-bow may not be as sensitive to anatomical changes 

as the arbitrary earpiece face-bow. 

Goska and Christensen conducted a similar study to 

to the present study, in which they compared the positions 

of maxillary cast permanent first molars in three planes of 

space, using four different face-bow techniques. A true hinge 

face-bow determined axis point was chosen as a baseline 

against which to compare the other three arbitrary face-bow 

techniques. 28 They found that deviations between this baseline 

and the other three face-bow mountings ranged from 1.5 

mm to 4 mm. 28 They found that deviations between the true 

hinge face-bow and the arbitrary earpiece face-bow ranged 

from 1.9 mm to 3.8 mm. Like the authors of the present 

study, they concluded that variations in the arbitrary earpiece 

face-bows might have resulted from naturally occurring 

variations in ear anatomy or the fact that the arbitrary 

earpiece face-bow is an average measurement. 28 

In general, the present study suggests that error introduced 

from arbitrary earpiece face-bow hinge axis location 

may produce occlusal discrepancies caused by malpositioning 

of the maxillary cast. The present study differs from 

other previous studies in that it evaluates changes at the 

occlusal level of the maxillary cast, as opposed to looking 

at the joint level when comparing arbitrary and true hinge 

mounting techniques. This study also differs from previous 

studies in that it does not measure the occlusal discrepancies 

that result from contacts during the mandibular arc of 

closure, since the mandibular cast was not incorporated into 

the measurements. 

Zuckerman, in analog tracing the arc of the incisal edge, 

verified that no A-P change occurred in the arc of closure, as 

long as the mandible rotated along the accurate hinge axis. 

However, when an error in the arbitrary earpiece face-bow 

hinge axis occurred anterior to the true hinge, the incisor arc 

of closure was anterior to the actual arc of closure, and when 

the arbitrary earpiece face-bow hinge axis occurred posterior 

to the true hinge axis, the opposite effect occurred. Errors in 

the vertical position of the arbitrary earpiece face-bow hinge 

axis were found to produce the largest A-P discrepancies 

upon mandibular closing41 (Figure 9). 


Figure 9-a True hinge mandibular cast vs. estimated hinge 

maxillary cast: True hinge mounting. 

Figure 9-b True hinge mandibular cast vs. estimated hinge 

maxillary cast: Estimated hinge mounting substituted for true 

hinge maxillary mounting. 

Zuckerman found that an anterior incisor displacement 

of 1.5 mm could occur if the arbitrary hinge axis was off from 

the true hinge axis by approximately 10 mm. 41 Although the 

method for the present study does not incorporate the mandibular 

cast arc of closure, wax bite thickness, or condylar 

positioning, it is interesting to note that the largest discrepancy 

in maxillary cast position occurred in the A-P direction 

with a mean difference greater than 3 mm in all three areas 

measured (maxillary right and left first permanent molar and 

the upper right permanent central incisor). 

Gordon et al conducted a mathematical study to calculate 

the amount of cusp height and mesiodistal error at the 

second molar that results from arbitrary earpiece face-bow 

hinge axis location 5 mm and 8 mm anterior, superior, posterior, 

and inferior to the true hinge axis. 6 They concluded 

that incorrect location of the hinge axis caused a positional 

change in the occlusal relationship between the maxilla and 

the mandible, resulting in various premature contacts. De-

pending upon the direction in which the arbitrary earpiece 

face-bow hinge axis was displaced from the true hinge axis, 

the premature contacts occurred either anterior or posterior 

to the actual arc of closure. Total error that could occur at 

the second molar cusp ranged from 0.15 mm of open cuspal 

space to 0.4 mm of excess cuspal height. The mesiodistal 

error of the second molar cusps ranged from 0.51mm toward 

the distal to 0.52 mm toward the mesial. 6 Brotman also 

found that a 0.09-mm A-P discrepancy would occur between 

occluding casts if the arbitray earpiece face-bow hinge axis 

was improperly located by as much as 3 mm from the true 

hinge point. Brotman concluded that if the arbitrary earpiece 

face-bow hinge axis is incorrectly placed superior to the true 

hinge axis, the lower cast will occlude in a more protrusive 

direction, with premature contacts on the anterior teeth. 

If the arbitrary earpiece face-bow hinge axis is incorrectly 

placed inferior to the true hinge axis, the lower cast will occlude 

in a more distal direction, with premature contacts on 

the posterior teeth. 43 This conclusion resembles the findings 

of Gordon et al. Weinberg and Fox drew similar conclusions; 

the values they obtained for calculated horizontal error in 

cusp heights closely resembled each other. 35,44 This suggests 

that errors of several millimeters in axis location might produce 

occlusal errors that are clinically intolerable on the part 

of the patient. 43 

The authors of the present study found a mean difference 

in incisor position of 3.04 mm. The occlusal discrepancies 

found in the present study suggest that a range greater 

than 5 mm existed between hinge axis points located with 

the arbitrary earpiece face- bow mounting and the true hinge 

face-bow. The discrepancy in maxillary cast position found 

in this study might possibly introduce a change in the closure 

of the mandible into occlusion. The problems caused 

by the occlusal errors resulting from inaccurate location of 

the hinge axis point are illustrated in Figure 10. The photos 

suggest an exaggerated discrepancy between the two casts 

because two completely different face-bow techniques were 

used. They serve to illustrate occlusal error that may result 

from error in maxillary cast position. In some cases, however, 

the autorotated mandibular casts closed with only a 

small degree of occlusal error (Figure 9). Other casts showed 

severe positional changes resulting in larger occlusal errors 

when this was attempted. (Figure10). 

Figure 10-a Mounted maxillary estimated cast vs. 

true hinge mounted maxillary cast: True hinge mounting. 

Figure 10-b Mounted maxillary estimated cast vs. 

true hinge mounted maxillary cast: Estimated hinge mounting 

substituted for true hinge maxillary mounting. 

It may be difficult to detect which patients have arbitrary 

earpiece face-bow hinge points naturally located within 

5 mm of their true hinge point. Therefore, if any degree of 

accuracy is needed or if any change in vertical dimension, 

such as an occlusal equilibration or orthognathic surgery, is 

planned, use of a true hinge axis face-bow should be considered. 

Previous studies have suggested that location of a 

kinematic true hinge axis point prior to treatment for dentulous 

patients who require extensive treatment saves time and 

results in a more satisfactory occlusion. 6 The present study 

found a statistically significant difference in the maxillary 

cast position in all three planes of space between the two 

face-bow techniques compared. 

Conclusions 

1. Statistically significant differences (p < .001) were 

found between the true hinge face-bow mounted maxillary 

cast and the estimated earpiece face-bow hinge mounted max- 


53

illary cast in the vertical dimension, with a mean of 2.19 mm 

for the maxillary right first molar, 2.45 mm for the maxillary 

left first molar, and 1.90 mm for the maxillary right central 

incisor. 



cast and the estimated earpiece face-bow hinge mounted 

maxillary cast in the A-P direction, with a mean difference 

of 3.82 mm between the maxillary right first molars, 3.10 

mm between the maxillary left first molars, and 3.05 mm 

between the maxillary right central incisors. 



cast and the estimated earpiece face-bow hinge mounted 

maxillary cast in the transverse dimension, with a 2.23-mm 

difference between the maxillary right first molars and a 

2.60-mm difference between the maxillary left first molars. 

4. This study found that there is a significant difference 

between the arbitrary earpiece face-bow hinge axis and 

the true hinge face-bow hinge aixs. Thus, when an arbitray 

earpiece face-bow hinge axis transfer is used, the maxillarymandibular 

complex is placed in an incorrect position in the 

articulator. The end result is a lack of functional harmony. ■ 

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27. Wood DP, Korne PH. Estimated and true hinge axis: a comparison 

of condylar displacements. Angle Orthod. 1992;(62): 167-175.

28. Goska JR, Christensen LV. Comparison of cast positions by using 

four face-bows. J Prosthet Dent. 1988;(59): 42-44. 

29. Simpson, JW, Hesby RA, Pfeifer DL, Pelleu GB. Arbitrary mandibular 

hinge axis locations. J Prosthet Dent. 1984;(51):819-823 

30. Lauritzen AG, Bodner GH. Variations in location of arbitrary and 

true hinge axis points. J Prosthet Dent. 1961;(11): 224-229. 

31. Palik JF, Nelson DR, White JT. Accuracy of an earpiece face-bow. J 

Prosthet Dent. 1985;(53): 800-804. 

32. Schulte JK, Rooney DJ, Erdman AG. The hinge axis transfer procedure: 

a three-dimensional error analysis. J Prosthet Dent. 1984;(51): 

247-251. 

33. Morneburg TR, Proschel PA. Predicted incidence of occlusal errors 

in centric closing around arbitrary axes. Int J Prosthod. 2002;(15): 

358-364. 

34. Ricketts, RM, Perspectives in the Clinical Application of Cephalometrics. 

Angle Orthod. 1981;(51): 115-150. 

35. Weinberg LA. An evaluation of the face-bow mounting. J Prosthet 

Dent. 1961;(11): 32-42. 

36. Adrien P., Schouver J., Methods for minimizing the errors 

in mandibular model mounting on an articulator. J Oral Rehab. 

1997;(24):929-935. 

37. Brotman DN. Hinge axes, part I: the transverse hinge axis. J Prosthet 

Dent. 1960;(10): 436-440. 

38. Preston JD. A reassessment of the mandibular transverse horizontal 

axis theory. J Prosthet Dent. 1979; 41: 605-613. 

39. Teteruck WR. Lundeen HC. The accuracy of an ear face-bow. J 

Prosthet Dent. 1966;(16):1039-1046. 

40. Walker PM. Discrepancies between arbitrary and true hinge axes. J 

Prosthet Dent. 1980;(43): 279-285. 

41. Zuckerman GR. The geometry of the arbitrary hinge axis as it 

relates to the occlusion. J Prosthet Dent. 1982;(48): 725-733. 

42. Collett Henry A. The movements of the temporomandibular 

joint and their relation to the problems of occlusion. J Prosthet Dent. 

1955;(5): 486-496. 

43. Brotman DN. Hinge Axes, ,part II: geometric significance of the 

transverse axis. J Prosthet Dent. 1960;(10): 631-636. 

44. Fox SS. The significance of errors in hinge axis location. J Am Dent 

Assoc. 1967;(74):1262-1272. 

45. Williamson EH, Evans DL, Barton WA, Williams BH. The effect 

of bite plane use of terminal hinge axis location. Angle Orthod. 

1977;(47): 25-33. 


55

Notes 

56 Notes

The Effect of Tooth Wear on Postorthodontic Pain Patients: Part 2 

Jina Lee Linton, DDS, MA, PhD, ABO ■ Woneuk Jung, DDS 

Jin a Le e Li n T o n , ddS, ma, Phd, abo 

jinalinton@hotmail.com 

■ Graduated from Yonsei University 

(DDS, PhD), 1986 

■ Graduated from Columbia University, 

SDOS, 1988 

■ Graduated from Columbia University 

Orthodontic Department (MA), 1991 

■ Private Practice in Seoul, Korea, 

1991–present 

Wo n e u K Ju n G , ddS 

■ Graduated from Dan Kook 

University, 1991 

■ Private practice in Seoul, Korea, 

1991–present 

Introduction 

Tooth attrition is classified as tooth disease under the Inter- 

national Classification of Diseases, published by the World 

Health Organization. According to Jablonski, tooth attrition 

takes place when tooth-to-tooth contact, as in mastication, 

occurs on the occlusal, incisal, and proximal surfaces. 1 It is 

differentiated from tooth abrasion (the pathologic wearing 

away of the tooth substance by friction, as brushing, bruxism, 

clenching, and other mechanical causes) and from tooth 

erosion (the loss of substance caused by chemical action 

without bacterial action). 

In reality, the wear may be related to a combination of 

factors including attrition, abrasion, and erosion; that is, 

physical-mechanical and chemical effects can have an impact 

on the loss of physiologic and habitual tooth surface morphology. 

2 Grippo et al state that three physical and chemical 

mechanisms are involved in the etiology of tooth surface lesions. 

These mechanisms are stress, corrosion, and friction. 

The various types of dental lesion are caused by these mechanisms 

acting either alone or in combination. Friction, including 

abrasion (which is exogenous) and attrition (which is 

endogenous), leads to the dental manifestation of wear. Corrosion 

leads to the dental manifestation of chemical or elec- 

Summary 

Malocclusion and occlusal interference in excursive movement is the major 

cause of pathologic tooth wear. Tooth wear starts with shortening of the anterior 

teeth. As interference in mandibular movement increases, the posterior 

teeth gradually become more flat. Recognizing tooth wear before and after 

orthodontic treatment is important for retention of the treated result and for 

ensuring functional occlusion. For this reason, orthodontic treatment should 

be detailed and completed with restorative rehabilitation of the lost tooth 

material. 

trochemical degradation. Stress, which results in compression, 

flexure, and tension, leads to the dental manifestation 

of microfracture. 3 

Loss and excessive wear of hard dental tissues is a permanent 

problem of the dentition, especially in the modern 

man; it is found in almost all age groups. Tooth wear is an 

inherent part of the aging process; it occurs continuously but 

slowly throughout life. In some individuals, tooth wear occurs 

more rapidly than in others, leading to severe morphologic, 

functional, and vital damage to the teeth, which cannot 

be considered normal. 4 Hand et al found that in a sample of 

520 adults, 84.2% had enamel attrition, 72.9% had dentin 

attrition, and 4.2% had severe attrition. 5 In cases of severe 

attrition, Sivasithamparam et al found that 11.6% of 448 

adult patients had either near-pulpal exposures or frank pulpal 

exposures. 6 

Schneider and Peterson found that 15% of children 

demonstrate tooth wear due to bruxism. 7 Most of the prevalence 

studies in Europe and North America indicate that the 

prevalence of wear on enamel in children is common (up to 

60% involvement), while the prevalence of exposed dentin 

varies from 2% to 10%. 8,9 


57

Case Reports 

The six cases below show individual clinical cases with various 

severity of attrition with or without treatment. 

Case 1: Attrition Occurred With no Orthodontic Treatment 

An 11-year-old female came in for checkup in April 2006, 

at which time the upper lateral incisor edges and canine tips 

showed wear (Figure 1). She had class I canine and molar 

relationships and a 3-mm overbite and overjet (April 2006). 

When she came back for orthodontic treatment 3 years later 

(January 2009), the wear on the laterals and canines had 

progressed significantly (red arrows). 

Figure 1 Attrition occurred with no orthodontic treatment. 

Case 2: Attrition Occurred During Orthodontic Treatment 

A 12-year-old male had a crossbite on the left laterals and an 

open bite on the central incisors (Figure 2). His canines and 

molars were in class I relationship (September 2002). After 

a year and a half without treatment, the upper left canine 

showed slight wear on the mesial side (January 2004). After 

8 months of fixed appliance therapy, that canine showed 

marked flattening on the tip (October 2004). 

Figure 2 Attrition occurred during orthodontic treatment. 

58 Linton, Jung | The Effect of Tooth Wear on Postorthodontic Pain Patients: Part 2 

Case 3: No Attrition Occurred During Orthodontic Treatment 

A 17-year-old male had class II div. 2 malocclusion (Figure 

3) and displayed no wear on the upper right canine tip (September 

1995). After 22 months of treatment with mandibular 

advancement surgery, the sharp canine tip remained (July 

1997). 

Figure 3 No attrition occurred during orthodontic treatment. 

Case 4: Slight Attrition Occurred During Orthodontic 

Treatment 

A 13-year-old male with class I malocclusion came in presented 

with sharp upper canine tips (June 1998). After 1½ 

years of fixed-appliance therapy (January 2000), the right 

canine tip remained intact (blue arrow), while the left canine 

tip showed wear. A photograph taken 2 years posttreatment 

(January 2002) showed wear on the right canine 

tip (Figure 4).

Figure 4 Slight attrition occurred during orthodontic treatment. 

Case 5: No Attrition Occurred During or Following 

Orthodontic Treatment 

A 24-year-old female came in for treatment of bimaxillary 

dentoalveolar protrusion (June 1998). The canine tip remained 

the same immediately after orthodontic treatment 

(April 2001) and 7 years posttreatment (April 2008). This patient 

had no apparent anterior tooth attrition over the 10-year 

observation period (Figure 5). On lateral excursive movement, 

canine guidance existed with adequate separation of posterior 

teeth on both the chewing and the nonchewing sides. 

Figure 5 No attrition occurred during or after orthodontic treatment. 

Case 6: Attrition Occurred During Orthodontic Treatment 

A 13-year-old male came to the clinic in January 2000 for 

treatment of protruding upper incisors. The patient’s face 

showed a protrusive upper lip and a normal-size mandible, 

with no apparent asymmetry. He had class II malocclusion 

with maxillary dentoalveolar protrusion, severe crowding 

in the upper and lower arches, and a constricted maxillary 

arch. The upper right canine had not erupted due to lack of 

space, even though the root had almost formed (Figure 6). 

Figure 6 Preorthodontic treatment photographs and x-rays. 

Figure 6-a Front facial 

smiling photograph. 

Figure 6-b Lateral facial 

photograph showing lip 

protrusion and strained 

mentalis muscle. 

Figure 6-c Right lateral intraoral photograph 

showing class II molar relationship in MIP. 

Figure 6-d Front intraoral photograph in MIP showing 

crowding and crossbite in the upper right lateral incisor. 


59

Figure 6-e Left lateral intraoral photograph in MIP showing 

class II molar relationship and retained deciduous canine. 

Figure 6-f Panoramic x-ray. The upper left canine showing 

root apex almost formed, but not erupted, due to lack of space. 

Figure 6-g Lateral cephalogram showing slightly 

retrusive mandible and protrusive upper incisors. 

Jarabak’s cephalometric analysis showed a strong counterclockwise 

growth tendency expressed in such measurements 

as a posterior facial height-anterior facial height ratio 

of 70%, a long ramus height in comparison to the posterior 

cranial base length, and a small Y-axis-to-SN angle (Table 1). 


Table 1 Jarabak’s analysis of case 6 in January 2000. 

The maxillary arch was rapidly expanded with a fixed- 

type expander, which was retained for 6 months. Growth 

modification of the maxillary protrusion was accomplished 

simultaneously with a high-pull headgear for 10 months. The 

diagnostic study models mounted before and after headgear 

therapy clearly showed the effect of the growth modification 

treatment (Figure 7). 

Figure 7 Mounted models of the case before and after the 

first phase of growth modification treatment. The models were 

mounted on a semiadjustable articulator with estimated 

face-bow transfer and with centric relation bite registration 

records. The class II relationship of the first molars (blue lines) 

in January 2001, was improved compared to the molar 

relationship of the case in January 2000. 

Subsequent to headgear therapy, the four first premolars 

were extracted, and the patient received fixed-appliance 

therapy for the following 20 months. Class I canine and 

molar relationships were achieved with maximum anchorage 

in the upper arch and moderate anchorage in the lower 

arch in December 2002. The patient’s facial appearance was

improved, with retraction of the upper anterior teeth and 

favorable mandibular growth (Figure 8). 


smiling photograph. 

Figure 8 Postorthodontic treatment records. 


photograph showing 

improvement in profile 

compared to Figure 1b. 

Figure 8-c Right lateral intraoral photograph showing 

that class I canine and molar relationships were achieved. 

Figure 8-d Front intraoral photograph showing 

that approximately 2 mm of overjet was achieved. 

Figure 8-e Left lateral intraoral photograph showing 

that class I canine and molar relationships were achieved. 

Figure 8-f Maxillary arch showing alignment 

without any extraction spaces left. 

Figure 8-g Panoramic x-ray showing overcorrection in 

root angulation of the canines and developing third molars. 


61

Figure 8-h Lateral cephalogram. 

Figure 8-i Superimposition of cephalometric tracings before 

(black line) and after (red line) orthodontic treatment shows 

that maximum anchorage control of the upper molars was 

accomplished. The maxilla and the mandible grew 

downward and forward as predicted. 


The patient returned to the clinic for correction of lower 

anterior tooth crowding at age 20 in April 2008 (Figure 9). 

Figure 9 Four-year retention photographs. 


smiling photograph showing 

well-developed gonial angle. 


photograph. 

Figure 9-c Right lateral intraoral photograph showing that 

class I canine and molar relationships were retained. 

Figure 9-d Front intraoral photograph showing that the 

lower dental midline was shifted 2 mm to the left.

Figure 9-e Left lateral intraoral photograph 

showing end-on class II canine relationship. 

Figure 9-f Panoramic x-ray. 

Figure 9-g Lateral cephalogram. 

Figure 9-h Superimposition of the cephalometric tracings 

after orthodontic treatment (red line) and 4-year retention 

(green line), showing that there was little change in the 

soft-tissue and hard-tissue structures. 

Upon clinical examination, wear on the maxillary canine 

tips was noted as being quite severe for his age. Upon further 

questioning, the patient complained of occasional headache 

and pain in the area of the temporomandibular joint (TMJ). 

His static occlusion showed 1.5 mm of overbite at the central 

incisors and no overbite on the left lateral incisor. The lower 

anterior teeth were tipped to the left side, resulting in a lower 

midline shift to the left side. Dentin exposures were present 

on the upper lateral incisal edges and the lower anterior 

teeth. The upper and lower first molars also showed marked 

wear on the cusp tips. Upon excursive movement of both 

right and left sides of the madible, the posterior teeth on the 

chewing side showed simultaneous contacts—that is, group 

function—and teeth on the nonchewing side showed harmful 

contacts (Figure 10). 


63

Figure 10 Mandibular movements. 

Figure 10-a Due to wear on the canine tip, there are multiple 

tooth contacts on the right chewing side and harmful contacts 

on the left nonchewing side during the right chewing movement. 

Figure 10-b Incisive movement indicates 

multiple contacts on the posterior teeth. 

Figure 10-c Due to wear on the canine tip, there are multiple 

tooth contacts on the left chewing side and harmful contacts on 

the right nonchewing side during the left chewing movement. 


The patient’s records were reviewed to compare the 

amount of tooth wear at age 15 immediately after orthodontic 

treatment (December 2002) with the amount of tooth 

wear at age 20 (Figure 11). 

Figure 11 Comparison of tooth wear over a 5-year period. 

Progression of tooth wear from 1.5 mm of vertical overbite 

in the upper and lower canines in December 2002 down to 

minimum vertical overbite in April 2008. 

(Red arrows indicate flattened anterior teeth.) 

The canine tips already showed wear at age 15. Progression 

of tooth wear was evident; 1.5 mm of vertical overbite in 

the upper and lower canines in December 2002 was reduced 

down to minimum vertical overbite in April 2008. The occlusal 

views showed the beginning of dentin exposure on the 

upper lateral incisors and the canines. The first molar wear 

caused no obvious incisal changes but the progression of the 

wear was definitely observable as wider wear facets and dimples 

on the molar cusp tips in April 2008 (Figure 12). 

Figure 12 Occlusal views of tooth wear. Wear on the posterior 

teeth is less apparent than wear on the anterior teeth. On close 

examination, tooth wear (red arrows) is shown as facets or 

dimples on the cusp tips.

All available intraoral photographs that had been taken 

in the past were put together to analyze the event of tooth 

wear in this patient (Figure 13). 

Figure 13 The event of upper canine wear during orthodontic 

treatment. The right canine shows definite wear (red arrows) 

during fixed-appliance therapy. The sharp anatomy (blue circle) 

of the left canine tip at the time of eruption is shown in the 

photograph (May 2000). It was gone before the 

fixed-appliance therapy. 

The upper right canine showed no wear before the 

initial stage of fixed-appliance therapy in June 2001. The 

canine wear occurred sometime during the following 8 

months, and further wear seemed to have occurred between 

February 2002 and December 2002. The upper left canine 

erupted with sharp anatomy in May 2000. However, the tip 

was worn down already on the day of bracket bonding, and 

the wear progressed during the fixed-appliance therapy. In 

the absence of anatomy at the cusp tips and incisal edges, as 

in Figures 3-c and 3-e, proper anterior guidance and canine 

guidance in movement would not have taken place (Figure 

14). This in turn would have caused further wear with the 

passage of time, as shown in Figures 6 and 7. 10 

Figure 14 Mandibular movement of the mounted models. 

Figure 14-a Intraoral movement shown in Figure 5-a was 

reproduced with models mounted on a semiadjustable 

articulator in SCP. There were nonchewing-side interferences 

of the functional cusps of the upper left molars (red arrows). 

Figure 14-b Intraoral movement shown in Figure 5-b was reproduced 

using models. There were nonchewing-side interferences 

of the functional cusps of the right upper molars (red arrows). 

Stable condylar position (SCP) could not be recorded in 

the presence of dysfunction of the masticatory system, 11 so 

a maxillary anterior-guided orthosis12 was prepared and the 

patient wore it for 2 months, until all clinical signs and symptoms 

of TMJ dysfunction disappeared. The orthosis (Figure 

15) allowed the condyles to assume their superior, anterior, 

and medial (SAM) positions in intimate contact with the 

thinnest part of the biconcavity of the disc, and made possible 

the diagnosis of a SCP from the maximum intercuspal 

position (MIP). The SCP was recorded with Axi-Path recording, 

so the mounted models would arc close in centric. 13,14 

Figure 15 Maxillary anterior guided orthosis. The patient 

wore the removable plate continuously until all the 

symptoms disappeared and SCP was obtained. 


65

Subtractive coronaplasty 15 was done on the posterior 

teeth to achieve equal stops and maximum intercuspation in 

SCP, and to preserve the natural tooth forms (Figure 16). 

Figure 16 Before and after coronaplasty. 

Figure 16-a The maxillary arch after coronaplasty shows 

that coronaplasty does not necessarily flatten the occlusal 

surfaces. Rather, it can redefine the anatomy. 

Figure 16-b The mandibular arch after coronaplasty also 

shows redefined anatomic form of the posterior teeth. 

Anterior maxillary and mandibular teeth were built up 

with wax on the diagnostic casts to relegate all eccentric 

tooth contacts to the anterior teeth (Figure 17). 

The additive coronaplasty was done by duplicating the 

wax-up of the casts on the anterior teeth with composite 

resin (Figure 18). 16 

Figure 17 Wax-up on the mounted model to achieve 3 mm to 4 

mm of vertical overbite and 2 mm to 3 mm of horizontal overjet. 

Figure 18 Additive coronaplasty was done with a hybrid-type 

composite resin on each anterior tooth according to the 

wax-up in Figure 12. 


The average unworn maxillary central incisor is approx- 

imately 12 mm and the mandibular central incisors are 10 

mm according to the American Academy of Cosmetic Dentistry 

(AACD). In the patient’s case, they were 12 mm and 

7.7 mm and were restored to 12.3 mm and 9.8 mm respectively 

(Figure 19). 17 

Figure 19 Measurements of the teeth before and after positive 

coronaplasty. The upper central incisors were 12.0 mm long 

and became 12.3 mm long. The lower central incisor was 

7.7 mm long and became 9.8 mm long. 

According to Lee, adequate anterior guidance can be obtained 

with incisor vertical overlap of 3 mm to 4 mm and 

horizontal overlap of 2 mm to 3 mm. 18 Initially in April 2008 

the patient’s MIP and SCP did not coincide and his overjet 

was 2 mm. In SCP the overjet increased to 3.5 mm, which was 

corrected to 2 mm with additive coronaplasty (Figure 20). 

Figure 20 Overjet change after coronaplasty. When MIP 

and SCP did not coincide, the overjet was 2 mm. In SCP, 

the overjet increased to 3.5 mm, which was corrected 

to 2 mm with additive coronaplasty. 

Only after additive coronaplasty could a complete elimination 

of eccentric occlusal interferences be achieved with 

excursive movements of the mandible (Figure 21).

Figure 21 Mandibular movement after coronaplasty. 

Figure 21-a In the right chewing movement, both the chewing 

and the nonchewing sides show sufficient clearance between 

the upper and lower posterior teeth (blue arrows). 

Figure 21-b In the left chewing movement, both the chewing and 

the nonchewing sides show sufficient clearance (blue arrows). 

With coronaplasty the patient’s bite was stable, and the 

patient was pleased with his smile and with the overall appearance 

of his face (Figure 22). 

The abnormal tooth wear the patient demonstrated before 

coronaplasty was due to improper incisal guidance and 

canine guidance. Since tooth wear progresses much faster in 

the dentin layer than in enamel, his entire dentition would 

have become significantly shorter over the next 10 to 20 

years, if no intervention had taken place. The patient’s occlusion 

was completed with coronaplasty, and the longevity 

and stability of his dentition were greatly enhanced. 

Discussion 

At the present, the majority of dentists believe that teeth 

can successfully compensate for the loss of tissue by migration 

and elongation, and that these do not disturb the basic 

functions of the masticatory system (mastication, speech, 

and swallowing). 19 However, some researchers have argued 

that anatomical tooth form plays an important role in the 

proper function of the masticatory system. 17,18 Knight and 

et al conducted a longitudinal study on 223 orthodontically 

treated patients 20 years posttreatment. They found that 

there was a strong relationship between incisal and occlusal 

tooth wear during the mixed dentition and subsequent 

wear of the adult dentition. 20 Tooth wear that occurred during 

the mixed dentition in these subjects actually occurred 

on the permanent incisors. Even though the malocclusion 

was corrected, the loss of tissue due to wear in the previously 

affected teeth persisted. Consequently, the patients’ 

incomplete anterior and canine guidance systems continued 

to influence their permanent dentition. 

Figure 22 Comparison of the case before and after coronaplasty. 

Figure 22-a Full-smile facial photograph taken after 

coronaplasty shows that the patient’s smile became 

more esthetically pleasing. 

Figure 22-b Lateral facial photographs taken 

before and after coronaplasty show little change. 

With regard to interferences in mandibular movement, 

Masatoshi and Masanori studied occlusal factors in relation 

to TMD in 146 young adults; they concluded that molarguided 

occlusion patterns were associated with a high risk 

of TMD. 21 All subjects with TMD had nonchewing interferences 

in border excursions and in tooth-dictated excursions. 

Without additive coronaplasty to restore the lost volume of 

tooth material, complete elimination of interferences may 

not be possible, nor may it be possible to maintain the optimal 

health of the teeth. 16 As we saw in case 6, the teeth 

were too worn down to allow for adequate function, and 

the post-orthodontic result was an incomplete occlusion vulnerable 

to relapse. The patient’s TMJ symptoms would have 

persisted, and the attrition process would have accelerated 

once the dentin layer was exposed. Tooth wear that occurred 

while the patient was receiving treatment was unavoidable in 

this case. Early intervention of malocclusion in mixed denti- 


67

tion might have enabled us to circumvent pathologic tooth 

wear while the patient was undergoing treatment? 

In canine guidance, the horizontal forces are minimized 

by limiting the contact of the supporting cusps with their opposing 

fossae at or near their intercuspal position. All other 

lateral contacts are prevented by the steeper inclination of 

the canines. This causes the chewing movement to be more 

vertical in the frontal view. Case 5 exemplifies the preservation 

of tooth material in the presence of functional occlusion. 

Upon lateral excursive movements, the canine guidance 

provided sufficient clearance in the posterior teeth. 

Many of our orthodontic patients already have worn 

canines and incisors. Occlusal interferences, premature contacts, 

and habitual bruxism and/or clenching all may act as 

stressors. Tooth contact during swallowing occurs 2,400 

times a day, according to Straub23 and Kydd. 24 These repetitive 

static and cyclic occlusal loads could also cause wear 

on the anterior, as well as the posterior, teeth. Although it is 

difficult to quantify the amount of tooth wear precisely, especially 

in cross-sectional studies, orthodontists can appraise 

attrition of the incisal edges and canine tip most easily from 

intraoral photographs. Why should orthodontists be aware 

of tooth wear? What happens if the dentist ignores if they 

ignore the problem? These are important questions, because 

any patient who is not informed of tooth surface loss is put 

at risk of having no choice in treating what can become a 

severe condition. ■ 

References 

1. Jablonski, S. Jablonski’s Dictionary of Dentistry. 2nd ed. Philadelphia: 

Saunders, 1992. 

2. Litonjua L, Andreana S, Bush PJ, et al. Tooth wear: attrition, erosion, 

and abrasion. Quintessence Int. 2003;(34):435-446. 

3. Grippo J, Simring M, Schreiner S. A new perspective on tooth surface 

lesions. J Am Dent Assoc. 2004;135(8):1109-1118. 

4. Badel T, Keros J, Šegović S, Komar D. Clinical and tribological view 

on tooth wear. Acta Stomatol Croat. 2007;41(4):355-365. 

5. Hand J, Beck J, Turner K. The prevalence of occlusal attrition and 

considerations for treatment in a noninstitutionalized older population. 

Spec Care Dentist. 1987;(7):202-206. 

6. Sivasithamparam K, Harbrow D, Vinczer E, et al. Endodontic sequelae 

of dental erosion. Aust Dent J. 2003;(48):97-101. 

7. Schneider P, Peterson J. Oral habits: considerations in management. 

Pediatr Clin North Am. 1982;(29):523-546. 

8. Dugmore C, Rock W. The prevalence of tooth erosion in 12-year-old 

children. Br Dent J. 2004;196(5):279-282. 


9. Bardsley P, Taylor S, Milosevic A. Epidemiological studies of tooth wear 

and dental erosion in 14-year-old children in north west England, part I: 

the relationship with water fluoridation and social deprivation. Br Dent J. 

2004;197(7):413-416. 

10. Cordray F. Centric relation treatment and articulator mountings 

inorthodontics. Angle Orthod. 1996;66(2):153-158. 

11. Lee R. Jaw movements engraved in solid plastic for articulator controls, 

part I: recording apparatus. J Prosthet Dent. 1969;(22):209-224. 

12. Academy of Prosthodontics. Glossary of prosthodontic terms. 

J Prosthet Dent. 2005;94(7):10-92. 

13. Lundeen H. Centric relation records: the effect of muscle action. 

J Prosthet Dent. 1974;31(3):244-253. 

14. Crawford S. Condylar axis position, as determined by the occlusion 

and measured by the CPI instrument, and signs and symptoms of temporomandibular 

dysfunction. Angle Orthod.1999;69(2):103-116. 

15. Hunt K. Bioesthetics: Working with nature to improve function and 

appearance. Am Acad Cosmet Dent. 1996;12(2):45-50. 

16. Hunt, K. Full-mouth rejuvenation using the biologic approach: an 11year 

case report follow-up. Contemp Esthet Restor Pract. 2002;6(6):1-6. 

17. Lee R. Esthetics and its relationship to function. In: Rufenacht CR, ed. 

Fundamentals of Esthetics. Chicago: Quintessence; 1990:137-209. 

18. Hunt K, Turk M. Correlation of the AACD accreditation criteria and 

the human biologic mode. J Cosmet Dent. 2005;21(3):120-131. 

19. Ash M, Nelson S. Dental Anatomy, Physiology and Occlusion. 8th ed. 

St Louis, MO: Saunders; 2003. 

20. Knight D, Leroux B, Zhu C, Almond J, Ramsay D. A longitudinal 

study of tooth wear in orthodontically treated patients. Am J Orthod 

Dentofac Orthop. 1997;112(6):17-18. 

21. Masatoshi K, Masanori F. Occlusal factors associated with temporomandibular 

disorder based on a prospective cohort study of young adults. 

Prosthod Res Pract. 2006;5(2):72-79. 

22. Jemt T, Lundquist S, Hedegard B. Group function or canine protection. 

J Prosthet Dent. 1982;(48):719-724. 

23. Straub W. Malfunctions of the tongue. Am J Orthod. 1960;(40):404-420. 

24. Kydd W. Maximum forces exerted on the dentition by the perioral and 

lingual musculature. J Am Dent Assoc. 1957;(55):646-651.

Physiologic Treatment Goals in Orthodontics 

Andrew Girardot, DDS, FACD 

and R e W Gi R a R d o T , ddS, Facd 

ragfishing@hotmail.com 


Dentistry (DDS), 1968 


Dentistry, Dept. of Orthodontics 

(certificate in orthodontics), 1972 

■ Part-time Faculty University of 

Colorado, School of Dentistry, 

Dept. of Orthodontics 

■ Cofounder, codirector and faculty, 

Roth Williams USA, 1997-present 

Introduction 

For the better part of a hundred years, orthodontists have 

used Angle’s classification as a means of communication. 

When we say “Class I,” orthodontists share the same image, 

which is generally a positive concept of how teeth should fit 

together. There certainly can be a Class I case with problems, 

but Class I is the first major step in describing optimal tooth 

relationships. To this day, Angle’s Class I describes a morphologic 

treatment goal for the orthodontic specialty. 

Why do we not have a similar physiologic treatment 

goal? Often we talk about “occlusion” in orthodontics, but 

it clearly means different things to different people. The term 

occlusion lacks the communication value of Class I. A “good 

occlusion” is a nebulous term that varies depending on the 

person using it. We have a communication problem. We enjoy 

general agreement, and hence communication clarity, 

regarding morphology, but this is not the case for physiology. 

It would certainly be of value to our patients and the 

orthodontic specialty if we had a clear definition of what 

constitutes optimal physiology or “good occlusion.” 

As in all biologic systems, the structural elements of 

the human gnathic system have evolved to perform best un- 

Summary 

Angle’s class I has long served the orthodontic specialty as a morphologic 

treatment goal and a means of communication. Certainly a physiologic 

treatment goal would be of equal value. There are sound data to define and 

support such a physiologic goal, which can help orthodontists to better serve 

their patients, communicate with other dental professionals, and avoid numerous 

clinical problems. 

der certain conditions of form and function. For example, 

there is considerable evidence to support a clear definition 

of healthy function for the temporomandibular joint in its 

loaded state, such as during a swallow. When loaded, the 

condyle should be positioned upward, forward and midsagittally. 

This definition of optimal joint position is agreed 

upon by most authorities1-15 and is well supported by the 

literature. 16-36 Okeson defines this as the “most musculoskeletally 

stable position of the mandible.” 7(112) There also are 

data indicating the optimal relationship of the condyle, disc, 

and eminence when the mandible is moving into or out of 

the loaded position. In this condition, there should be constant 

contact between the condyle, disc, and eminence. 37-40 

There are numerous data indicating that neuromuscular 

function is highly influenced by tooth contacts and tooth positions. 

41-55 For example, as the mandible moves into and out 

of intercuspation, guidance from properly positioned anterior 

teeth aids in separating the posterior teeth. This reduces 

the activity of the powerful elevating muscles, which, in turn, 

downloads the system while facilitating constant contact between 

the condyle, disc, and eminence. 39,43,46,47,55-64 

Thus, current data point to an optimal physiologic rela- 


69

tionship between the teeth, the joints, and the neuromusculature. 

This information provides a physiologic treatment goal 

for the orthodontist, a summary of which can be made by analyzing 

the system in loaded and unloaded conditions. When 

loaded, eg, during a swallow, the condyles are fully seated 

upward and forward in the fossae, the elevating muscles are 

active, and the dentition is in full intercuspation. 41,55,62,63,65,66 

When unloaded, the condyles remain in firm and constant 

contact with the disc and eminence, elevating muscles are inactive 

and positioning muscles (eg, lateral pterygoids) are active, 

posterior teeth are out of contact, and the anterior teeth 

play a major role in guiding mandibular movements. 67-75 

Given a reliable perspective of optimal static and dynamic relationships 

between the teeth, joints, and neuromusculature, 

we can consider some additional principles regarding gnathic 

function. There are at least three reasons why the intercuspal 

position is important. First, the positions and the shapes of 

the teeth determine mandibular movements at and near the 

intercuspal position. 7,50,61,76-100 Second, when the mandible is 

brought to full intercuspation in a functionally healthy system, 

the powerful elevating muscles are active and the system 

is heavily loaded; the bulk of the resultant force is absorbed 

by posterior teeth. 32,50-52,101-103 Third, condylar position is determined 

by the dentition at intercuspation. 61,83,104-106 

An additional important factor well supported in the literature 

is the clinical observation that the neuromusculature 

is exquisitely programmed to guide the mandible to the intercuspal 

position80,85-100,107 ; the intercuspal position is dominant 

over condylar position. 61,83,103,105,106,108-110 Thus, asking 

a patient to “bite down” provides no dependable information 

as to where the condyle is positioned. Moreover, efforts 

to identify the seated condylar position through clinical 

maneuvers such as manipulating the mandible are not reliable. 

28,111-116 To quote the master clinician Dr. Thomas Basta, 

“Don’t believe what you see in the mouth.” 2 Thus the value 

of using interocclusal devices such as cotton rolls, anterior 

jigs, and splints to deprogram the neuromusculature. 

If we are to apply these physiologic principles to the 

practice of orthodontics, we need additional information 

besides that which we have traditionally used; for example, 

techniques that record the optimal or “seated” position of 

the condyle. Currently there are numerous such techniques 

employed in restorative dentistry. Many clinicians use a hard 

stop at the incisor midline to separate the posterior teeth, 

along with a soft posterior material that can be hardened 

thermally or chemically. When the patient bites against the 

hard anterior stop and the neuromusculature seats the condyles 

superioranteriorly, the posterior material is hardened, 

and the musculoskeletally stable position of the mandible is 

recorded (Figure 1). 

70 Girardot | Physiologic Treatment Goals in Orthodontics 

Figure 1 The anterior stop is hard and flat; it separates the 

posterior teeth to create appropriate space for a recording 

medium. The patient is instructed to close firmly, which 

seats the condyles to the musculoskeletally stable 

position of the mandible. 

The information then must be transferred from the patient 

to a device that will allow study and treatment planning 

of the gnathic system in three dimensions. Currently, 

the articulator appears to be the best tool for this purpose, 

although computer-generated three-dimensional technology 

may replace the articulator in the near future. Casts mounted 

on an articulator provide invaluable physiological information 

for diagnosis and treatment planning. For example, 

numerous studies show that there is nearly always vertical 

distraction of the condyle when the patient closes to intercuspation. 

33,113,117-122 It is all but impossible to record, analyze, 

and treatment plan this vertical discrepancy without the 

use of a device such as an articulator. 

Joint images are another tool that can serve orthodontists 

with regard to physiologic treatment. Tomograms, as 

first advocated by Ricketts, have provided an effective way 

to study the health of the temporomandibular joint and the 

position of the condyle in the fossa. 123-125 At present, cone 

beam CT is a more effective way to study the temporomandibular 

joint, as it provides a more-lucid, three-dimensional 

view of joint structures. 36 

There are sound data to support the concept that optimal 

gnathic function can be defined and used as an evidence-based 

treatment goal. There is little doubt that this 

would also aid communication between orthodontists and 

other dental professionals. In addition, knowledge of gnathic 

physiology is of substantial value to orthodontists in that it 

helps them to recognize and avoid myriad problems that occur 

in everyday practice. ■

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74 

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Effect of Gnathologic Positioner Wear on Maximum 

Intercuspation CR Disharmony 

Wesley M. Chiang, DDS, MS ■ Theodore Freeland, DDS, MS 

■ Richard Kulbersh, DMD, MS, PLC ■ Richard Kaczynski, BS, MS, PhD 

We S L e y m. ch i a n G , ddS, mS 

■ MA Candidate, Orthodontic Dept., 

University of Detroit Mercy School 

of Dentistry 

The o d o R e FR e e L a n d, ddS, mS 

tdfortho@freelandorthodontics.com 

■ Adjunct Professor, Orthodontic 

Dept., University of Detroit Mercy 

School of Dentistry 

■ Director Roth/Williams USA; 

■ Private Practice, Gaylord, MI 

Ric h a R d Ku L b e R S h, dmd, mS, PLc 

■ Program Director, Orthodontic 

Dept., University of Detroit Mercy 

School of Dentistry 

Ric h a R d Ka c z y n S K i , bS, mS, Phd 

■ Statistician, Dept. of Psychiatry, 

Yale University School of Medicine 

Introduction 

Centric relation (CR) refers to a physiologic position of the 

mandible when the condyles are located in the superoanterior 

position in the articular fossae, fully seated and resting 

against the posterior slopes of the articular eminences with 

the discs properly interposed. 1 It is a reproducible position 

that is obtained independent of the occlusion by manipulating 

the mandible in a purely rotary movement about the 

transverse horizontal axis. 2 

Orthodontic treatment is aimed at achieving static goals 

from Andrews’ six keys to normal occlusion and the functional 

scheme of mutually protected occlusion recommended 

by Stuart and Stallard. 3,4 In the 1970s, Roth introduced gna- 

Summary 

The goal of a gnathological approach in orthodontics is to achieve a functional 

occlusion, in which the mandible can close into maximum intercuspation (MI) without 

deflecting the condyles from centric relation (CR). Gnathologic positioners are 

used at the end of orthodontic treatment to settle the occlusion while maintaining 

MI-CR harmony. The objective of this prospective study was to examine the effect 

of gnathologic positioners on MI-CR discrepancy for patients treated with the Roth 

gnathological approach. 

Methods.The sample consisted of 26 consecutively finished cases in a gnathologically 

oriented practice. All cases were treated with a gnathological treatment approach, 

using the Roth prescription straight-wire appliance. A gnathologic positioner was 

delivered at the time of debonding and was worn for a period of 2 months. Pre- and 

postpositioner records were taken. These included a maximum-intercuspation wax 

bite; a two-piece Roth power centric CR bite registration; and upper and lower models 

mounted using a true hinge transfer and CR bite. The control group consisted of 8 

randomly selected finished cases in the orthodontic clinic at the University of Detroit 

Mercy and was retained with Hawley retainers. MI-CR discrepancy was measured 

with a condylar position Indicator (CPI). 

Results. Results indicate a statistically significant improvement in MI-CR discrepancy 

in the right horizontal, right vertical, left vertical, and transverse planes after 2 months 

of gnathologic positioner wear. The amount of condylar distraction in these 4 measurements 

showed statistically significant improvement and came within the envelope 

of susceptibility. 

Conclusions.The positioner and control groups tend to change differently over time 

in the vertical and horizontal planes, with the positioner group improving and the 

control group getting worse. In the transverse plane, gnathologic positioners improve 

the result of orthodontic treatment with respect to condylar axis distraction. 

thological concepts into orthodontic treatment. 5,6,7 The goal 

of a gnathological approach in orthodontics is to achieve a 

functional occlusion, in which the mandible can close into 

maximum intercuspation (MI) without deflecting the condyles 

from CR. 8 Dr. Roth believed that a large discrepancy 

between MI and CR can lead to breakdown in the stomatognathic 

system, because the condyles are distracted from 

the glenoid fossae when the teeth come into occlusion. Signs 

and symptoms of occlusal disharmony include temporomandibular 

joint pain-dysfunction syndrome, occlusal wear and 

bruxism, excessive tooth mobility associated with periodontal 

disease, and movement or relapse of tooth positions. 9 

Occlusal discrepancies, if associated with joint compression, 


75

can also lead to condylar resorption. 10 

The clinical acceptable difference between CR and MI 

in terms of condylar position is approximately 1.0 mm anteroposteriorly, 

1.0 mm vertically, and 0.5 mm transversely. 

11,12,13,14 The condylar position indicator (CPI) has been 

used to accurately record condylar movements. 15 A comparison 

between pretreatment and posttreatment records in patients 

treated in a gnathologically oriented practice showed a 

statistically significant reduction in MI-CR discrepancy in all 

3 planes of space. 16 The posttreatment records were obtained 

before delivery of the gnathologic positioner. 

The purpose of this study was to examine the effect of 

gnathologic positioners on MI-CR discrepancy for patients 

treated with the Roth gnathological approach. The effectiveness 

of gnathologic positioners can be determined if there 

is a decrease in MI-CR discrepancy following 2 months of 

positioner wear. 

Research Design and Methods 

The positioner group consisted of 26 consecutively finished 

cases in a gnathologically oriented practice (Theodore Freeland, 

DDS, MS, Gaylord, Michigan). The sample consisted of 

15 males and 11 females. The average age was 15 years and 

8 months. All cases were treated with a gnathological treatment 

approach, using the Roth prescription straight-wire 

appliance (GAC, Glendora, California). 12 Seven cases were 

treated with 4 premolar extractions, while 19 cases were 

treated with nonextraction. Four weeks prior to the debonding 

appointment, prepositioner records were taken (time 1). 

The records included upper and lower alginate impressions 

in rim lock trays, a true hinge face-bow transfer; an MI wax 

bite taken using 10x pink wax (Myoco Industries, Inc, Philadelphia, 

Pennsylvania); and CR bite registration taken using 

a two-piece Roth power centric method with Delar blue wax 

(Delar Corporation, Lake Oswego, Oregon) (Figure 1). 

Figure 1 Two-piece CR bite – anterior segment (A). 

Two-piece CR bite – posterior and anterior segments (B). 

MI bite (C). Two-piece CR and MI bite (D). 

The models were poured with a vacuum mixed white stone 

(Whip Mix Corporation, Louisville, Kentucky) and mounted 

with Whip Mix mounting plaster (Whip Mix corp, Louisville, 

Kentucky), using a true hinge transfer and CR bite 

(Figures 2,3). 

Figure 2 True hinge axis. 

Figure 3 True hinge mounted models with two-piece CR bite. 

Fabrication of Gnathologic Positioner 

The gnathologic positioner was fabricated using Oralastic 

80 silicone. The true hinge positioner set up is fabricated 

according to posterior determinants (angle of the articular 

eminence and Bennett side shift). At time 1, a second set of 

upper and lower alginate impressions was taken and poured 

with white stone. The models were left unmounted, while the 

first set of models was mounted using true hinge face-bow 

transfer and CR bite. Unmounted models were used to fabricate 

the gnathologic positioner, using the mounted models 

as a reference. Teeth were separated from the models, and 

brackets were ground off the teeth. Mandibular teeth were 

set to an occlusal plane with proper curve of Spee and curve 

of Wilson, and set on arc of closure in CR. The upper teeth 

were set to the lower teeth in accordance with ideal overbite/ 

overjet (OB/OJ). 

At the debonding appointment, the braces were removed, 

and the gnathologic positioner was delivered. The arc of clo- 

76 Chiang, Freeland, et al | Effect of Gnathologic Positioner Wear on Maximum Intercuspation CR Disharmony

sure was first checked in the mounting on the true hinge ar- 

ticulator and then checked intraorally with and without the 

positioner. The patient was instructed to wear the positioner 

full time for the first 3 days (with the exception of eating and 

brushing). After the first 3 days, the patient was instructed to 

wear the positioner at night, with 4 hours of positioner exercise 

during the day. If the positioner should fall out during 

the night, the patient was instructed to wear the positioner 

for 6 hours during the day. 

Positioner Exercise and Wear Protocol 

The patient was instructed to bite into the positioner just 

enough to seat all of the teeth and to fully engage the teeth in 

the positioner. The patient was instructed to bite with pressure 

for about 10 seconds and then to relax for about 15 

seconds. The exercise was done in 15-minute intervals, with 

15 to 20 minutes of rest in between. For nighttime wear, the 

patient was instructed to put the positioner into the mouth 

and close the mouth to engage the positioner as much as possible 

without putting pressure on the positioner. 

The gnathologic positioner was checked for fit and arc 

of closure at 1, 2, and 4 weeks after delivery. After 2 months 

of positioner wear, postpositioner records were taken (time 

2). These consisted of the same records that had been taken 

at time 1. Upper splint and lower spring retainers were then 

delivered. 

The control group consisted of 8 randomly selected 

finished cases in the orthodontic clinic at the University of 

Detroit Mercy. The control group was not preselected with 

regard to MI-CR discrepancy at debond. At the debonding 

appointment (time 1), braces were removed and records 

were taken. Upper and lower Hawley retainers were delivered, 

and the patient was instructed to wear them full time. 

After 2 months of Hawley retainer wear, records were taken 

again (time 2). 

MI-CR discrepancy was measured with a CPI (Panadent 

Corporation, Grand Terrace, California) at times 1 and 2 for 

both groups (Figure 4,5). 

Results 

The mean differences between MI and CR of the articulators’ 

condylar axis position were recorded for the transverse, 

and separately for the right and for the left condyles in the 

vertical and anteroposterior (A-P) directions. Pre- and posttreatment 

measurements of MI-CR discrepancy of the control 

and positioner groups are summarized in Table 1. 

Figure 4 CPI registration with two-piece CR bite (A). 

CPI registration with MI bite (B). CPI Recording – transverse (C). 

CPI Recording – right (D). 

Figure 5 Condylar position indicator recording graph 

(CR – red dot, MI – blue dot). 


77

Measurements 

Table 1 MI-CR Discrepancy Assessment of Control and Positioner Groups. 

Mean 

(mm) 

Control Positioner 

(n=8) (n=26) 

Time 1 Time 2 Time 1 Time 2 

SD (mm) Mean 

(mm) 

SD 

(mm) 

Mean 

(mm) 

SD 

(mm) 

Table 2 Independent t-test for MI-CR Discrepancies of Control Versus Positioner Group. 

Mean 

(mm) 

Right AP 0.700 0.499 1.225 1.383 1.306 0.897 0.733 

Right vertical 0.863 0.407 1.238 0.845 1.217 0.969 0.623 

Left AP 0.750 0.864 1.625 1.201 0.867 1.010 0.671 

Left vertical 0.825 0.292 1.062 0.686 1.162 0.794 0.669 

Transverse 0.350 0.267 0.288 0.309 1.031 1.106 0.248 

As the table shows, pretreatment means for the control 

group were all within the clinical envelope of ± 1.0 mm for 

the A-P and vertical dimensions, and ± 0.5 mm for the transverse. 

Conversely, 4 out of 5 pretreatment means for the positioner 

group were outside this envelope; only the mean left 

A-P measurement, at 0.87, was within the clinical envelope. 

The control and positioner groups were then assessed by an 

independent t-test for any statistically significant pretreatment 

differences. As shown in Table 2, no differences were 

found between the two groups (0.08 of 0.05 

was reduced by a factor of 5 (for the 5 variable CPI readings: 

right A-P, right vertical, left A-P, left vertical, and transverse) 

to control experimentwide alpha and to avoid the risk of 

type I errors. Thus a significance level of α = 0.01 was used 

for each test of the condylar axis position measurements. The 

results indicated statistically significant differences between 

time 1 and time 2 for the positioner group in the right A-P (Δ 

= 0.57 mm, t = 3.03, p = .006); right vertical (Δ = 0.59 mm, 

t = 2.79, p = .009); left vertical (Δ = 0.49 mm, t = 3.05, p = 

.005); and transverse (Δ = 0.78 mm, t = 3.49, p = .002) measurements. 

There was no statistically significant difference in 

the magnitude of condylar distraction in the left condyle in 

the A-P direction (Δ = 0.20 mm, t = 0.92, N.S.). 

Mixed-design analyses of variance compared the positioner 

and control groups’ change in MI-CR discrepancy 

over time (Table 4). 

Table 4 Mixed Design Analysis of Variance for MI-CR Discrepancies from time 1 to time 2 between Control Versus Positioner Group. 

Using the adjusted significance level described above 

(α = 0.01), these comparisons between the 2 groups showed 

no statistically significant differences in any of the 5 CPI 

measurements. However, 4 of the 5 dimensions fell below 

Effect F* p 

Right AP Time 0.012 .915 

Time x group 6.096 .019 

Right vertical Time 0.266 .609 


Left AP Time 2.431 .129 


Left vertical Time 0.599 .445. 

Time x group 4.917 034 

Transverse Time 4.102 .051 

* df for all tests are 1, 32. 


the traditional α = 0.05 level. Graphical representations of 

the change in MI-CR discrepancy over time for the positioner 

and control groups are shown in Figures 6 through 10. 

Figure 6 Right horizontal MI/CR discrepancy. Figure 7 Right vertical MI/CR discrepancy. 


79

Figure 8 Left horizontal MI/CR discrepancy. 

Figure 9 Left vertical MI/CR discrepancy. 

Figure 10 Transverse MI/CR discrepancy. 

Discussion 

Results of the present study indicate a statistically significant 

improvement in MI-CR discrepancy in the right horizontal, 

right vertical, left vertical, and transverse planes 

with 2 months of gnathologic positioner wear. The condylar 

axis distraction differences in the left horizontal planes 

were not statistically significantly different. Before positioner 

wear, the mean right horizontal, right vertical, left vertical, 

and transverse measurements were 1.306 mm, 1.217 mm, 

1.162 mm, and 1.031 mm respectively, and fell outside the 

± 1.0 mm vertical and horizontal as well as the ± 0.5 mm 

transverse distraction envelope proposed by Crawford, Utt 

et al, and Slavicek. 12,13,14 Following 2 months of positioner 

wear, the amount of condylar distraction in these 4 measurements 

showed statistically significant improvement and 

came within the distraction envelope. Before positioner wear, 

3 patients (11.5%) had MI-CR discrepancy that fell within 

the envelope of susceptibility in all 5 of the measurements 

examined, while 11 patients had all 5 measurements within 

the envelope after positioner wear (42.3%). Reducing MI- 

CR discrepancies is an important treatment goal in the gnathological 

philosophy, and the use of gnathologic positioner 

is essential to achieving this goal. 

Although these changes were nonsignificant when compared 

to change in the control group, the level of significance 

in the right horizontal, right vertical, and left vertical 

planes was very close to the significance level of 0.01 used 

for this study, and below the more common 0.05 level of 

significance. Figures 6, 7 and 9 show a similar pattern with 

reduction in MI-CR discrepancy over time with positioner 

wear, while the group with the Hawley retainers shows an 

increase in MI-CR discrepancy. This trend is observed in 3 of 

the 5 measurements studied (right horizontal, right vertical, 

and left vertical planes). The positioner and control groups 

tend to change differently over time in the vertical and horizontal 

planes, with the positioner group improving and the 

control group getting worse. This is consistent with Roth’s 

claim that general retention protocols with Hawley-type appliances 

following orthodontic therapy will tend to make 

MI-CR discrepancy worse, while gnathologic positioners 

will improve MI-CR discrepancy. Interestingly enough, all 

mean vertical and horizontal CPI measurements for the control 

group started within the distraction envelope of ± 1.0 

mm and finished outside the envelope following 2 months of 

Hawley retainer wear. 

The small sample size of the control group is a limitation 

of this study. A larger sample size would eliminate type II error 

and might show a statistically significant difference in the 

change in MI-CR discrepancy over time between the control 

and the positioner group. However, the p-values are below 

80 Chiang, Freeland, et al | Effect of Gnathologic Positioner Wear on Maximum Intercuspation CR Disharmony

the .05 level of significance in the right horizontal, right ver- 

tical, and left vertical planes. Furthermore, the MI-CR pattern 

is observed, suggesting that this is not a purely random 

phenomenon. Since the control group was small, there is the 

possibility of an underpowered study. 

In the transverse plane, there appears to be no difference 

between the 2 groups over time. A condylar axis distraction 

in the transverse plane is more sensitive to clinical problems 

than a condylar axis distraction in the horizontal and vertical 

planes. 17,18,19 It appears that gnathologic positioners improve 

the result of orthodontic treatment with respect to condylar 

axis distraction. 

Conclusion 

Results of the present study indicate a statistically significant 

improvement in MI-CR discrepancy in the right horizontal, 

right vertical, left vertical, and transverse planes with 2 

months of gnathologic positioner wear. The amount of condylar 

distraction in these 4 measurements showed statistically 

significant improvement and came within the envelope 

of susceptibility. The positioner and control groups tend to 

change differently over time in the vertical and horizontal 

planes, with the positioner group improving and the control 

group getting worse. In the transverse plane, gnathologic positioners 

improve the result of orthodontic treatment with 

respect to condylar axis distraction. ■ 

References 

1. Okeson JP. Management of Temporomandibular Disorders and Occlusion. 

3rd ed. St Louis, MO: Mosby; 1998:109-125. 

2. Schmitt ME, Kulbersh R, Freeland T, et al. Reproducibility of the 

Roth power centric in determining centric relation. Semin in Orthod. 

2003;9(2):102-108. 

3. Andrews LF. The six keys to normal occlusion. Am J Orthod. 

1972;(62):196-309. 

4. Stuart CE. Good occlusion for natural teeth. J Prosthet Dent. 

1964;(14):716-724. 

5. Roth RH. Temporomandibular pain dysfunction and occlusal relationships. 

Angle Orthod. 1973;(43):136-153. 

6. Roth RH. Treatment mechanics for the straight wire appliance. In: 

Graber TM, Swain BH, eds. Orthodontics: Current Principles and 

Techniques. St Louis, MO: Mosby; 1985:665-716. 

7. Roth RH. Occlusion and condylar position. Am J Orthod Dentofac 

Orthop. 1995;(107):315-318. 

8. Pangrazio-Kulbersh V, Poggio V, Kulbersh R, et al. Condylar distraction 

effects of two-phase functional appliance/edgewise therapy versus 

one-phase Gnathologically based edgewise therapy. Semin in Orthod. 

2003;9(2):128-139. 

9. Roth, RH. The maintenance system and occlusal dynamics. Dent 

Clin North AM 1976;20:761-788 


retrusion-idiopathic condylar resorption, part II. Am J Orthod. 

1996;(110):117-127. 

11. Roth RH. Functional occlusion for the orthodontist, part I. J Clin 

Orthod. 1981;(15):32-51. 

12. Crawford SD. Condylar axis position, as determined by the occlusion 

and measured by the CPI instrument, and signs and symptoms of 

temporomandibular dysfunction. Angle Orthod. 1999;(69):103-116. 

13. Utt TW, Meyers CE Jr, Wierzba TF, Hondrum SO. A three-dimensional 

comparison of condylar position changes between centric relation 

and centric occlusion using the mandibular position indicator. Am 

J Orthod Dentofac Orthop. 1995;(107):298-308. 

14. Slavicek R. Interviews on clinical and instrumental functional 

analysis for diagnosis and treatment planning, part I. J Clin Orthod. 

1988;(22):358-370. 

15. Lavine D, Kulbersh R, Bonner P, Pink FE. Reproducibility of the 

condylar position indicator. Semin in Orthod. 2003;9(2):96-101. 

16. Klar NA, Kulbersh R, Freeland T, et al. Maximum intercuspationcentric 

relation disharmony in 200 consecutively finished cases in a 

gnathologically oriented practice. Semin in Orthod. 2003;9(2):109- 

116. 

17. Kulbersh R, Dhutia M, Navarro M, et al. Condylar distraction 

effects of standard edgewise therapy versus gnathologically based 

edgewise therapy. Semin in Orthod. 2003;9(2):117-127. 

18. Freeland T, Kulbersh R. Orthodontic therapy using the Roth gnathologic 

approach. Semin in Orthod. 2003;9(2):140-152. 

19. Roth RH, Rolfs DA. Functional occlusion for the orthodontist, part 

II. J Clin Orthod. 1981;(15):100-123. 


81

Notes 

82 Notes


83

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